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A  TOPICAL 


SYNOPSIS  OF  LECTURES 


ANIMAL  PHYSIOLOGY 


HENRY  SEWALL,  Ph.  D.,  M.  D., 

PROFESSOR  OF  PHYSIOLOGY  IN  THE  UNIVERSITY  OF  MICHIGAN. 


THIRD  EDITION,  REVISED  AND  ENLARGED, 


ANN  ARBOR,  MICH. : 
SHEEHAN  &  COMPANY. 

1888. 


ii  0  Km  I 

I   r  /  if 


The  Courier  Printing  House,  Ann  Arbor,  Mich. 


AUTHOR'S  NOTE  TO  THE  FIRST  EDITION. 

This  skeleton  of  a  course  of  lectures  on  physiology  has  been 
prepared  at  intervals,  with  the  sole  object  of  helping  students 
to  fix  the  attention  upon  the  main  facts  ot  the  subject.  The 
topics  have  served  simply  as  points  of  departure  in  the  lecture 
room,  and  no  effort  has  been  made  to  render  the  "  Synopsis  " 
clear  to  any  for  whom  the  spaces  between  the  paragraphs  have 
have  not  already  been  filled  in.  The  author  has  been  burdened 
with  no  desire  for  originality,  and  for  good  reasons  the  admira- 
ble text-books  of  Professor  Martin  and  of  Dr.  Foster,  especially 
the  latter,  have  frequently  been  followed  in  both  order  and 
substance  in  the  preparation  of  these  notes. 


Digitized  by  the  Internet  Archive 

in  2010  with  funding  from 
Columbia  University  Libraries 


http://www.archive.org/details/topicalsynopsiso1888sewa 


I.   THE  OBJECT  OF  PHYSIOLOGY  AND  THE  FUNCTIONS  OF  LIV- 
ING MATTER. 

Physiology  is  the  study  of  the  chemistry  and  physics  of  the 
living  body. 

Physiologically,  Life  is  the  sum  of  the  functions  of  matter 
called  Protoplasm. 

Protoplasm  is  made  up  of  the  elements  C,  H,  O,  N,  traces 
of  P  and  S ;  some  inorganic  salts.  Contains  much  water  and 
probably  residues  of  proteids,  fats,  and  carbohydrates. 

Protoplasm  has  remarkable  capacity  for  absorbing  water. 

To  make  protoplasm  needs  building  material  and  building 
energy. 

In  the  animal  both  are  supplied  by  the  food  and  oxygen 
taken  in. 

In  the  green  plant  sunlight  supplies  energy. 

Living  protoplasm  is  continually  wasting  through  the  pro- 
cess of  oxidation. 

In  the  animal  the  waste  matter  contains  less  potential 
energy  than  the  food  ;  the  energy  difference  is  the  vital  force  of 
the  animal. 

The  general  functions  of  all  protoplasm  are  exhibited  by 
the  simplest  living  thing,  as  an  amwba,  or  white  blood  corpuscle. 

These  functions  are : 

Contractility. 

Spontaneity . 

Irritability. 

Conductivity . 

Co-ordination. 

Assimilation.  This  leads  to  Growth  by  Intussusception. 
Growth  stops  when  the  weight  of  egesta  equals  that  of 
ingesta.  As  the  amount  of  waste  matter  depends  upon 
the  mass  of  protoplasm  and  the  amount  of  matter  assimi- 
lated upon  its  surface,  growth  must  have  its  limit  accord- 
ing to  the  law  of  unequal  increase  of  mass  and  surface. 


—6— 

Reproduction. 

The  highest  animal  exists  first  as  an  egg,,  a  single  cell. 
Multiplication  of  cells  by  fission. 

The  body  is  composed  of  cells,  modified  cells  and  intercel- 
lular matter. 
Differentiation  of  tissues. 
Physiological  division  of  labor. 
Physiological  division  of  tissnes  into  : — 

Undifferentiated. 

Supporting. 

Nutritive  ;  including  assimilative  ;  secretory  ;  receptive  ; 
eliminative  ;  respiratory  ;  metabolic. 

Storage. 
'     Irritable. 

Conductive. 

Co-ordinating  and  Automatic. 

Motor. 

Productive. 

Reproductive. 


II.   THE  NATURE  OE  THE  LAWS  SUPPOSED  TO  RULE  THE  ACTIV- 
ITIES OF  THE  EODY. 

The  physiologist  studies  vitality  as  a  manifestation  of 
chemical  and  physical  energy  and  believes  the  laws  governing 
living  and  not  living  things  to  be  equally  inflexible. 

Energy  exists  in  two  states,  Potential,  and  Actual  or  Kine- 
tic. 

Potential  energy ;  represented  in  the  position  of  masses 
by  position  of  atoms  in  molecules. 

Kinetic  energy ;  represented  in  the  motion  of  masses  and 
of  molecules  and  atoms. 

The  different  kinds  of  energy. 

One  kind  of  energy  may  be  changed  into  another. 

Energy  is  indestructible. 

Energy  cannot  be  created. 

The  uses  of  a  machine  as  illustrated  by  the  steam  engine, 
the  pulley  and  the  watch  spring. 

The  principle  of  the  dissipation  of  energy. 

Consider  the  whole  history  of  the  energy  represented  in  a 
stone  thrown  by  the  arm  into  the  air. 


III.   THE  LYMPH  AND  BLOOD. 

The  fluid  parts  consist  of  food  matters  dissolved  and  al- 
tered by  digestion  and  the  activity  of  metabolic  tissues,  and  of 
the  products  of  tissue  change. 

LYMPH. 

The  tissue  elements  are  bathed  in  lymph. 

Physical  and  chemical  characters  of  lymph.  Lymph  cor- 
puscles. 

Lymph  derived  from  blood  by  diffusion. 

Nature  of  diffusion;  influence  of  temperature;  of  the  di- 
viding membrane  ;  of  the  concentration  and  composition  of  the 
diffusing  fluids. 

The  vital  condition  of  the  vascular  wall  as  effecting  the 
quantity  and  quality  of  substances  which  pass  through  it. 

The  quality  of  the  blood  as  affecting  the  formation  of 
lymph. 

Effect  of  blood-pressure  on  the  diffusion  and  filtration  from 
the  blood  vessels.    The  use  of  lymphatics  as  drainage  vessels. 

Various  directions  of  the  lymph  currents  of  diffusion  in  the 
body. 

Influence  of  the  blood  circulation  on  the  rate  of  diffusion 
by  the  supply  of  new  and  removal  of  waste  matter. 

Physical  and  vital  characters  of  lymph  corpuscles. 

Coagulation  of  lymph. 

BLOOD. 

Consists  physically  of  straw-colored  fluid  plasma  and  of 
solid  red  and  white  corpuscles. 

Relative  number  of  red  and  white  corpuscles.  Conditions 
of  its  physiological  variation. 

Size,  shape,  physical  and  vital  characters  of  white  cor- 
puscles. 

Number,  size,  shape,  physical  characters  and  function  of 
human  red  corpuscles. 


—9— 

Distinction  between  the  red  corpuscles  of  mammals  and  of 

other  vertebrates. 

Rouleaux  of  red  corpuscles  in  drawn  blood. 

Stroma  and  haemoglobin  of  red  corpuscles. 

Cause  of  opacity  of  blood.    "  Laky  "  blood  and  means  of 

producing  it. 

Composition  of  haemoglobin ;  haemoglobin  crystals. 

Characters  and  production  of  haemin  crystals. 

The  colorless  "blood-plates"  of  Bizzozero. 

COAGULATION  OF  BLOOD. 

Physical  changes  in  blood  on  coagulating;  jelly  stage; 
solid  clot;  cupping;  serum  ;  "resolution"  of  clot. 

Demonstration  of  fibrin  threads  in  the  clot  produced  on  a 
microscope  slide. 

Phenomena  of  clotting  in  a  capillary  tube. 
Effect  of  whipping  fresh  blood. 

(Plasma. 
Before  clotting  < 

(Corpuscles. 
Physical  components  of  blood 

(Clot=fibrin  + 
After  clotting  -|  corpuscles. 

(Serum. 

Whipped  blood=corpuscles+ serum. 

Red  corpuscles  have  nothing  to  do  with  coagulation. 

The  red  corpuscles  are  somewhat  heavier  than  the  plasma. 

The  huffy  coat;  its  nature  and  conditions  of  occurrence. 
When  blood  clots  sufficiently  slowly  the  corpuscles  settle  some- 
what in  the  liquid,  leaving  a  straw-colored  layer  of  plasma  at 
the  top.  When  coagulation  sets  in  the  upper  part  of  the  clot, 
being  free  from  corpuscles,  is  known  as  the  buffy  coat. 

The  reason  for  its  occurrence  in  blood  in  inflammatory  dis- 
ease. 

Relation  of  the  shape  of  the  clot  to  that  of  the  containing 
vessel. 

Color  of  clot  at  different  distances  from  the  free  surface. 

Uses  of  clotting  to  a  wounded  animal. 

Fibrin  does  not  exist  as  such  in  normal  blood. 

The  fluid  of  normal  blood  is  plasma  which  is  spontaneously 


—10— 

coagulable.     Serum  is  formed  only  by  the  process  of  coagula- 
tion ;  it  is  not  spontaneously  coagulable. 

CAUSES  OF  COAGULATION  AND  INFLUENCES  MODI- 
FYING IT. 

Old  theories  that  clotting  was  due  to  escape  of  ammonia; 
to  taking  up  of  oxygen. 

Significance  of  blood  clotting  under  mercury. 

Views  that  clotting  was  due  to  loss  of  heat ;  to  cessation  of 
circulation. 

Hypothesis  that  the  internal  coats  of  the  blood  vessels  pre- 
vent coagulation. 

Evidence  as  to  influence  of  internal  coat.  Formation  of 
thrombi  in  ligatured  vessels.  The  fluid  condition  maintained 
in  the  blood  of  carefully  excised  veins. 

View  that  blood  does  not  tend  to  clot  until  chemically  al- 
tered. The  retardation  of  clotting  by  oiling  the  walls  of  a 
vessel  into  which  an  animal  is  bled. 

Influence  on  coagulation  of  temperature;  of  strong  solu- 
tions of  mineral  salts;  of  stirring. 

White  blood  corpuscles  always  found  in  spontaneously 
coagulating  fluids. 

The  deposit  of  fibrin  around  a  foreign  object  in  flowing 
blood  is  preceded  by  accumulation  of  white  corpuscles. 

In  the  thin  clot  upon  a  microscope  slide  the  fibrin  threads 
start  from  white  corpuscles. 

In  slowly  clotting  horses'  blood  the  firmest  clot  is  at  the 
level  of  greatest  accumulation  of  white  corpuscles. 

Direct  observation  under  the  microscope  of  thrombus  for- 
mation in  a  frog's  tongue. 

The  disintegration  of  white  corpuscles  and  transition  forms 
on  drawing  blood  from  the  bod}'. 

All  that  has  here  been  said  of  the  white  corpuscles  prob- 
ably holds  true  for  the  colorless  "  blood-plates." 

Denis'  plasmine. 

Clotting  of  the  solution  of  plasmine. 

The  blood  clot,  fibrin,  is  probably  formed  from  a  proteid 
body,  fibrinogen,  a  constituent  of  the  blood  plasma,  under  the 


—11— 

action  of  a  Mr  in- ferment  which  is  produced  by  the  disintegra- 
tion of  the  colorless  corpuscles  (leucocytes  or  blood-plates,  or 
both.) 

Fibrinogen  is  found  in  solution  in  transudation  fluids;  is 
precipitated  by  saturating  with  salines ;  is  dissolved  by  dilute 
salines. 

Hastening  of  clotting  by  addition  of  fibrin-ferment  to  di- 
luted plasma. 

Necessity  of  salines  to  coagulation. 

The  action  of  the  fibrin-ferment. 

The  nature  of  animal  ferments;  conditions  of  action. 

The  origin  of  fibrin-ferment  and  method  of  obtaining  it. 

THE  TRANSFUSION  OF  BLOOD. 

Transfusion  as  practiced  on  the  isolated  hearts  of  the  frog 
and  dog. 

The  nature  of  the  foreign  blood  is  not  indifferent. 

Danger  in  direct  transfusion  of  clotting  in  the  transmission 
tube. 

Danger  of  injection  of  whipped  blood  because  of  its  con- 
tained fibrin  ferment. 

Experiments  illustrating  this  point. 

CHEMISTRY  OF  BLOOD. 

Average  specific  gravity  of  human  blood  is  1055;  relative 
weight  of  corpuscles  and  plasma. 

The  average  amount  of  fibrin  formed  in  the  coagulation  of 
blood  is  only  about  0.2  per  cent  of  its  weight. 

Reaction  of  blood  ;  its  variation  in  clotting. 

The  amount  and  kinds  of  gas  given  off  in  vacuum  by  a 
volume  of  blood  ;  by  serum. 

Chemical  composition  of  serum;  water,  90  p.  c;  proteids, 
(serum  albumin  and  paraglobulin),  8-9  p.  c. ;  fats,  salines  and 
extractives,  1-2  p.  c. ;  (the  principle  extractives  are  sugar,  urea 
and  lactic  acid). 

The  ash  of  serum  contrasted  with  the  ash  of  corpuscles. 

Chemical  composition  of  the  red  corpuscles  ;  of  the  white. 

HISTORY  OF  BLOOD  CORPUSCLES. 

Evidence  for  the  transitory  nature  of  the  corpuscles ;  varia- 

2 


—12— 

tion  in  number  at  different  times ;  probable  derivation  of  uri- 
nary and  bile  pigments ;  normal  number  quickly  regained 
after  hemorrhage. 

Origin  of  the  red  corpuscles  in  the  embryo :  metamorpho- 
sis of  mesoblastic  cells ;  transformation  of  white  corpuscles 
arising  in  the  liver  and  spleen ;  from  the  protoplasm  of  con- 
nective tissue  corpuscles. 

Origin  of  red  corpuscles  in  the  adult :  metamorphosed  from 
transitional  forms  of  white  corpuscles  found  in  the  spleen  and 
red  medulla  of  bones. 

Fate  of  red  corpuscles  :  probably  destroyed  in  the  spleen. 

White  corpuscles :  physiological  variation  in  number. 
Arise  in  lymphatic  glands  and  similar  organs.  They  probably 
serve  as  occasional  tissue  builders,  and  give  rise  to  red  cor- 
puscles. 

THE  QUANTITY  AND   DISTRIBUTION   OF   BLOOD   IN 

THE  BODY. 

About  one-thirteenth  of  body  weight  is  blood ;,  of  this  is 
contained : 

One-fourth  in  heart,  lungs,  large  arteries  and  veins. 
One-fourth  in  liver. 
One-fourth  in  skeletal  muscles. 
One-fourth  in  the  remaining  organs. 


IV.    THE  CHEMISTRY  OF  ANIMAL  TISSUES. 

All  the  activities  of  the  body  are  due  in  the  end  to  chemi- 
cal processes. 

The  body  is  composed  of  living  matter,  protoplasm,  and  of 
not  living  matter  which  is  made  by  protoplasm ;  otherwise,  the 
body  is  composed  of  Formative  and  of  Formed  matter.  In 
general,  formative  matter  exists  in  cells  while  formed  matter  is 
intercellular. 

The  molecule  of  protoplasm  probably  contains  residues  of 
proteids,  tats,  and  carbo  hydrates,  besides  salines  and  extrac- 
tives. 

PROTEIDS. 

These  form  the  principal  solids  of  active  tissues,  of  blood 
and  of  lymph.    They  must  form  a  part  of  the  food. 

The  molecule  is  very  complex ;  composed  of  many  atoms 
of  O,  H,  N,  C,  with  S  and  P. 

Proteids  are  amorphous. 

All  are  non  diffusible  except  Peptones. 

Mostly  coagulated  by  alcohol  and  ether. 

Soluble  with  change  in  strong  acids  and  alkalis. 

Chemical  reactions ;  xanthoproteic ;  Millon's  ;  caustic  soda 
and  copper  sulphate,  etc. 

CLASSES  OF  PROTEIDS. 

1.  Native  albumins ;  serum  and  egg  albumin.  Soluble  in 
water. 

2.  Derived  albumins  or  albuminates ;  acid  and  alkali 
albumin;  casein.  Not  soluble  in  water  but  in  dilute  acids  and 
alkalies.  Not  precipitated  by  boiling.  All  proteids  dissolved 
in  acid  or  alkali  become  albuminates. 

3.  Globulins;  globulin  ;  paraglobulin  ;  fibrinogen  ;  myosin. 
Not  soluble  in  water  but  in  dilute  salines ;  precipitated  by 
strong  salines. 


—14— 

4.  Fibrin.  Insoluble  in  water  and  dilute  salines.  Soluble 
with  difficulty  in  strong  salines  and  dilute  acids  and  alkalis. 

5.  Coagulated  proteids,  soluble  only  in  strong  acids  and 
alkalis. 

6.  Peptones.  Soluble  in  water.  Not  precipitated  by 
acids,  alkalis  or  boiling.  Diffusible.  Product  of  all  proteid 
digestion.    Many  varieties. 

NITROGENOUS  NON-CRYSTALLINE  BODIES  DERIVED 
FROM  AND  ALLIED  TO  PROTEIDS,  BUT  NOT  CAPA- 
BLE OF  REPLACING  PROTEIDS  IN  THE  FOOD. 

They  contain  the  elements  of  C,  H,  N,  O,  and  sometimes  S. 

They  give  some  of  the  chemical  reactions  for  proteids. 

Mucin  ;  a  secretion  of  mucous  epithelium. 

Chondrin ;  the  organic  basis  of  cartilage.  Its  solutions  set 
on  cooling. 

Gelatin ;  organic  basis  of  bone  teeth  and  tendon.  Solutions 
set  on  cooling. 

Elastin ;  from  elastic  tissue.   Its  solutions  do  not  gelatinize. 

Keratin  ;  from  hair,  nails,  epidermis. 

Nuclein  ;  from  nuclei  of  pus  corpuscles. 

COMPLEX  NITROGENOUS   FATS   CHIEFLY  FORMING 
PARTS  OF  NERVE  TISSUES. 

Lecithin  (C44H90NPO9). 

Protogon. 

Cerebrin. 

STORE  MATERIALS  LAID  UP  IN  THE  BODY  AS  FOOD 
FOR  THE  TISSUES;  FATS,  AND  CARBOHYDRATES. 

FATS. 

Neutral  fats  are  compounds  of  a  fatty  acid  with  glycerin. 
They  are  made  up  of  the  elements  C,  H,  O. 


—15— 

Insoluble  in  water.  Soluble  in  ether,  chloroform  and  hot 
alcohol. 

Are  decomposed  by  caustic  alkalis,  forming  soaps  with 
them,  leaving  the  glycerin  free. 


C3H5 


Palmitin  1  Y      Y  O, 

C16H360  )   3 


(  C3H5 
Stearin  \  Y  O, 

(018H350 

Olein  ■!  [      Y  O 


018H33oJ 


The  fats  occur  mixed  together  in  the  body.  Their  fusion 
points  differ.  Their  molecule  contains  much  more  C  and  H  in 
proportion  to  O  than  does  that  of  carbohydrates. 

CARBOHYDRATES. -Composed  of  C,  H,  and  O. 

Maltose  (C13H220llt  +  H_.0) ;  convertible  into  dextrose. 

Dextrose  or  grape  sugar  (06H1306);  capable  of  alcoholic 
fermentation  :  of  lactic  acid  fermentation. 

Lactose  or  milk  sugar  (G12H22011) ;  capable  of  lactic  acid 
fermentation. 

Inosit  (C6H1206)  ;  capable  of  lactic  acid  fermentation. 

Glycogen  (C6H10O5);  convertible  into  dextrose. 

Dextrin  (C6H10O5);  convertible  into  dextrose. 

SOME  OF  THE  SUBSTANCES  FORMED  IN  THE  BODY; 
FOR  THE  MOST  FART  "  WASTE  "  PRODUCTS  OF  TIS- 
SUE CHANGE. 

NON-NITROGENOUS  METABOLITES. 

Lactic  acid  (C3H603). 

Oxalic  acid  (H3C204),  in  oxalate  of  lime. 

Succinic  acid  (H3C4H404). 


—16— 
NITROGENOUS  METABOLITES. 

Urea  (NH2)2CO  ;  and  its  oxalate  and  nitrate. 

Uric  acid  (05H4N40  );  and  salts. 

Kreatin(C4H9N302). 

Kreatinin  (C4H7N30). 

Sarkin  (C5H4N40). 

(C6HltO) 
Leucin  ■<  r  O. 

(    NH2      ) 

Tyrosin  (C.H^NC^). 

Hippuric  acid  (09H9M03). 

Taurocholic  acid  (C26H  5  NS07). 

Glycocholic  acid  (C26H43jNOr). 


V,   EPITHELIUM,  CONNECTIVE  TISSUE,  BONE,  AND  PHYSIOLOGY 
OF  THE  SKELETON, 

EPITHELIUM. 

The  typical  animal  cell;  cell  membrane;  protoplasm; 
granules  ;  nucleus  and  nucleoli;  fibrillar  net  work. 

Scaly  or  squamous  epithelium  ;  epidermis  and  buccal  mu- 
cous membrane. 

Columnar  epithelium;  intestine. 

Pavement  epithelium ;  mesentety. 

Polyhedral  epithelium  ;  glands. 

Ciliated  epithelium ;  trachea. 

Difference  between  "  serous  "  and  "  mucous  ''  membranes. 

THE  CONNECTIVE  TISSUES. 

We  may  speak  of  the  temporary  skeleton,  composed  of 
epithelium  and  connective  tissue,  and  of  the  'permanent  skele- 
ton made  up  of  bone  and  cartilage. 

Function  and  distribution  in  the  body. 

White  fibrous  tissue  ;  physical  characters  ;  swelled  by  acids  ; 
distribution. 

Yellow  elastic  tissue;  physical  characters;  unaffected  by 
acids ;  distribution. 

Cement  substance. 

Connective  tissue  corpuscles  ;  varieties  of  form  and  func- 
tion ;  distribution. 

Riteform  or  adenoid  tissue. 

The  supporting  function  of  connective  tissue  elements  as 
illustrated  in  such  organs  as  the  brain. 

Gelatinous  tissue;  vitreous  humor;  umbilical  cord. 

Areolar  tissue  ;  composition  and  distribution. 

The  development  and  condition  of  fat  in  the  body. 

THE  PERMANENT  SKELETON.— CARTILAGE. 

Hyaline  cartilage ;  its  physical  characters ;  the  perichon- 


—18— 

drium;  contains  no  blood  vessels;  histological  appearance; 
cells  and  matrix;  method  of  formation  of  matrix;  transition 
forms  between  round  cartilage  cells  and  branched  periosteal 
cells;  distribution  and  function. 

Fibro-cartilage:  physical  and  histological  characters;  ac- 
tion of  acids;  distribution  and  function. 

Elastic  cartilage.  Parenchymals  cartilage ;  physical  and 
histological  character ;  unaffected  by  acids ;  distribution  and 
functions. 

THE  BONY  SKELETON. 

The  skeleton  is  at  once  the  fortress,  the  tools  and  weapons 
of  the  body. 

The  skeleton  should  be  made  of  parts  which  are  strong, 
light,  inflexible  and  symmetrical. 

Bones  are  composed  of  a  mixture  of  organic  and  earthy 
matter. 

The  former  is  flexible,  the  latter  stiff  and  brittle;  the  origi- 
nal size  and  shape  of  the  bone  are  retained  when  either  is 
removed. 

Two-thirds  of  the  weight  of  dry  bone  is  mineral,  chiefly 
0a3  2  (P  O  ). 

Mechanical  advantage  of  this  combination. 

THE  LONG  BONES. 

The  periosteum,  the  nutritive  membrane. 

The  expanded  articular  end  of  long  bones  allows  distribu- 
tion of  strain. 

The  advantage  gained  by  the  hollow  cylindrical  form  of 
the  bone. 

The  cancellated  extremities  and  the  red  and  white  marrow. 

Histological  structure  of  a  long  bone ;  the  perfection  of 
adaptation  for  firmness,  lightness  and  elasticity. 

THE  SKULL. 

Advantage  of  its  curved  shape. 

Fracture  at  the  base  of  the  skull  from  a  blow  upon  the  top. 

The  two  bony  tables  with  diploe  between. 

The  outer  bony  plate  is  thicker,  tough  and  fibrous. 


—19— 

The  inner  bony  plate  is  thinner,  dense  and  brittle. 

Use  of  diploe  in  deadening  jars. 

Use  of  the  sutures  in  limiting  the  extension  of  jars. 

THE  BACKBONE. 

The  separate  vertebrae  allowing  the  bending  of  the  spine 

Porous  structure  of  the  vertebrae. 

The   in  vertebral    pads   allow  bending  without    separation 
of  vertebrae,  and  deaden  jars. 

The  curved  shape  of.  the  spine  gives  it  a  wide  range  of 
elasticity. 

JOINTS. 

Distinction  between  the  axial  and  appendicular  skeleton. 

Ball  and  socket  joints. 

Hinge  joints. 

Pivot  joints. 

Gliding  joints. 

The  synovial  sac  and  its  influence. 

The  capsular  ligament. 

Bones  are  held  together  by  atmospheric  pressure. 

THE  BONY  LEVERS. 

The  mechanics  of  animal  movement. 
Lever  of  the  first  order ;    nodding  motion 

of  the  head I  F  \ 

p—      "        vv 

Lever  of  the  second  order;    raising  the 

bodv  on  the  toes  by  the  calf  muscles.      .        .  t  £ 

f  W 
Lever  of  the  third  order;  raising  of  fore- 
arm by  the  biceps  muscle      ....         \  £ 

\v        f        F 


VI.    THE  CONTRACTILE  TISSUES, 

AMOEBOID  CELLS.    CILIATED  CELLS.    MUSCLE. 

Contractility  is  a  function  of  Protoplasm  irrespective  of 
any  special  form  in  which  this  matter  may  be  found. 

Contractile  tissues  in  the  higher  animals  may  be  divided 
according  to  the  degree  of  their  specialization  of  function  into, 
— 1,  amoeboid  cells  ;  2,  ciliated  cells ;  3,  non-striated  muscle; 
4,  striated  muscle. 

All  visible  movements  of  higher  animals  are  due  to  the 
contraction  of  a  special  set  of  organs,  the  muscles,  which  are 
in  no  case  able  to  set  up  movements  spontaneously. 

The  amoeboid  cells  contract  throughout  their  body  sub- 
stance and  have  usually  the  power  of  locomotion. 

CILIATED  CELLS. 

Ciliated  ceils  are  fixed  and  are  usually  columnar  in  shape. 

The  free  margin  of  the  cell  is  thick  and  firm,  and  has  pro- 
jecting from  it  ten  to  thirty  long  protoplasmic  lashes,  the  cilia. 

The  movement  of  the  cilia  is  a  to  and  fro  whipping  motion. 

The  movement  is  two  or  three  times  quicker  in  one  direc- 
tion than  in  the  other. 

The  rate  of  movement  is  accelerated  with  elevation  of  tem- 
perature. 

Foreign  bodies  resting  on  the  cilia  are  urged  in  the  direc- 
tion of  the  more  rapid  motion. 

The  function  of  cilia  in  the  trachea  and  bronchi :  they 
cause  expulsion  of  foreign  particles  and  aid  the  mixture  of 
gases. 

The  movement  is  automatic  and  co  ordinated.  The  move- 
ment of  a  series  of  cilia  is  not  isochronous,  but  proceeds  in  a 
wave  form  along  the  row.  The  circulation  of  fluid  carried  on 
by  the  cilia  on  the  gills  of  the  fresh  water  mussel. 

The  impulse  to  the  movement  is  probably  conveyed  directly 
from  the  protoplasm  of  one  cell  to  that  of  the  next. 


—22— 

The  energy  produced  by  each  cell  is  calculated  as  sufficient 
to  raise  its  own  weight  each  minute  4^  metres. 

THE  MUSCLES. 

The  muscles  are  not  automatically  contractile. 

They  are  usually  red  in  color  from  contained  haemoglobin, 
but  the  color  is  not  essential.  The  pale  muscles  of  an  animal 
contract  more  quickly  than  the  red. 

There  are  two  great  groups  which  are  distinguished  histo- 
logically and  physiologically:  (1)  Plain  or  unstriated.  muscle; 
sometimes  called  visceral  or  organic  or  involuntary  muscle 
(2)  Cross-striated  muscle;  sometimes  called  skeletal  or  vol- 
untary muscle. 

All  striated  muscles  contract  quickly  after  a  short  latent 
period. 

All  non-striated  muscles  contract  slowly  after  a  long  latent 
period. 

The  visceral  or  involuntary  muscles  of  some  animals  are 
striated. 

HISTOLOGY  OF  NON-STRIATED  MUSCLE. 

The  flattened  lanceolate  cell;  the  rod-shaped  nucleus. 
The  method,  of  aggregation  of  the  muscle  cells,  and  their 
distribution  in  the  bod}^. 


THE  STRIATED  MUSCLE. 

The  manner  of  aggregation  of  muscle  and  other  tissues  as 
shown  in  the  cross  section  of  a  linb.  Each  muscle  is  made  up 
of  separate  bundles  of  fibres. 

The  fibres  may  be  oblique  or  parallel  to  the  long  axis  of 
the  muscle. 

The  length  of  the  individual  muscle  fibre  in  man  does  not 
exceed  one  inch  and  a  half. 

The  binding  together  of  fibres  in  fasciculi. 

The  union  of  muscle  with  tendon. 


—23— 

HISTOLOGY  OF  STRIATED  MUSCLE. 

The  muscle  fibre;  the  sarcolemma;  the  nuclei;  the  cross 
markings. 

The  cross  marking  is  due  to  alternate  bright,  dark  and  dim 
bands. 

The  juncture  of  muscle  fibres  by  their  beveled  endings. 

Two  modes  of  ending  in  tendon. 

The  greater  part  of  the  living  muscle  fibre  is  semi-fluid  in 
consistency. 

PHYSIOLOGY  OF  STRIATED  MUSCLE. 

The  function  of  the  muscle  fibre  is  to  contract  or  to  draw 
its  two  ends  nearer  together.  The  complex  results  which  are 
obtained  by  this  simple  means. 

Muscle  exists  in  the  body  in  two  natural  conditions,  in  an 
active  and  passive  state;  the  shape  and  elastic  properties  of 
the  muscle  are  different  in  the  two  conditions. 

The  shortening  of  the  muscle  is  active  and  due  to  distinct 
chemical  processes  ;  the  elongation  is  passive. 

The  shortening  is  caused  by  the  transverse  swelling  of  the 
fibres. 

The  muscle  does  its  work  by  shortening,  not  by  becoming 
thicker  in  contraction. 

The  muscle  does  not  perceptibly  alter  in  volume  in  con- 
traction. 

The  molecular  cause  of  contraction  is  probably  the  absorp- 
tion of  the  more  fluid  parts  of  the  muscle  fibres  within  defi- 
nite layers  of  more  solid  particles. 

Whatever  excites  a  muscle  to  contract  is  called  a  stimulus. 

The  contraction  begins  at  the  point  stimulated,  and  moves 
along  the  fibre  in  the  form  of  a  wave,  which  travels  in  the 
frog's  muscle  with  a  velocity  of  about  three  metres  per  second. 
The  wave  moves  slower  the  lower  the  temperature. 

THE  PHYSICAL  PROPERTIES  OF  MUSCLE. 

Compare  the  curve  of  elasticity  of  muscle  with  that  of  steel. 
Compare   the  curves  of  elasticity   of   resting  and   active 
muscle. 


—24— 

The  elasticity  of  resting  muscle  is  perfect  within  narrow 
limits. 

When  a  muscle  contracts  its  elasticity  decreases  and  its 
extensibility  increases. 

The  resting  muscles  in  the  body  are  always  slightly 
stretched  between  their  attachments.  Proof  of  this  and  signi- 
ficance for  the  welfare  of  the  body. 

The  protective  use  to  the  body  of  the  increased  extensibil- 
ity of  contracted  muscle. 

The  elasticity  of  the  muscle  enables  it  to  store  up  its 
energy  of  contraction. 

The  lifting  power  of  the  muscle  diminishes  with  contrac- 
tion. 

Show  how  in  the  movements  of  the  bony  levers  the  con- 
tractile energy  of  the  muscle  is  economized  according  to  the 
preceding  principle.  In  practice,  before  a  voluntary  contrac- 
tion, we  stretch  the  muscles  to  their  greatest  length. 


The  muscle  possesses  the  distinct  properties  of  contractility, 
conductivity  and  irritability. 

The  peculiar  nature  of  physiological  couductivity. 

Irritability  is  the  capability  possessed  by  some  tissues  of 
being  stirred  up  to  functional  activity  by  a  stimulus. 

Its  peculiarity  is  the  disproportion  between  the  amount  of 
energy  represented  in  the  stimulus  and  in  the  effect  produced. 

Irritability  is  decreased  by  low  temperature,  by  fatigue,  by 
various  drugs. 

The  old  view  that  contraction  of  muscle  was  due  to  swell- 
ing of  its  substance  by  the  in-fiow  of  'fc  animal  spirits." 

Proofs  of  the  independent  irritability  of  muscle :  contrac- 
tion of  embryonic  muscles  before  the  establishment  of  nervous 
connections;  the  "idio-muscular"  contraction;  the  nerve  free 
ends  of  the  sartorius ;  the  manner  of  action  of  curare. 

The  various  kinds  of  stimuli  capable  of  exciting  muscle; 
nervous;  mechanical;  thermal;  chemical;  electrical. 

The  character  of  a  muscular  contraction  caused  by  the 
application  of  a  galvanic  current. 

The  contraction  caused  by  a  single  induction  shock. 


—25— 

The  general  law  for  the  stimulation  of  irritable  tissues:  It 
is  only  the  change  of  intensity  of  a  stimulus  that  excites  an 
irritable  organ. 

The  most  favorable  rate  of  change  of  intensity  of  the  stim- 
ulus differs  for  different  kii;ds  of  tissues  ;  the  intensity  should 
vary  most  rapidly  for  nerve,  less  so  for  striped  muscie,  and  still 
more  slowly  for  unstriped  muscle. 

The  muscle  answers  a  single  stimulation  by  a  single  twitch 
or  contraction. 

The  contraction  is  prolonged  by  cold,  by  fatigue,  by  various 
drugs. 

The  prolonged  contraction  of  a  muscle  poisoned  with  vera- 
trin. 

The  "  graphic  method  "  of  recording  observations. 

The  curve  of  a  single  muscular  contraction;  the  latent 
period  of  stimulation;  the  phases  of  the  contraction  curve  ;  the 
"  contractur." 

The  latent  period  of  stimulation  is  the  interval  elapsing 
between  the  application  of  a  stimulus  and  the*  beginning  of 
contraction.  Its  average  duration  in  the  frog's  muscle  is  .01 
second.  During  the  latent  period  the  muscle  molecules  are 
undergoing  chemical,  electrical,  thermal  and  mechanical 
changes.  The  period  is  lengthened  by  cold,  by  fatigue,  by  in- 
creased load. 

The  "  contractur  "  is  due  to  the  "elastic  after  action  "  of 
the  muscle  substance,  not  to  vital  changes.  Influence  of  fatigue 
and  of  load  upon  the  contractur.  The  contractur  of  ths  flexor 
muscles  of  the  hand  after  clenching  the  fist.. 

Maximal  and  sub-maximal  single  contractions;  with  a  cer- 
tain strength  of  stimulus  the  muscle  gives  a  barely  visible 
contraction;  with  increase  of  stimulus  the  height  of  contrac- 
tion increases  to  a  certain  extent,  and  then  no  stronger  stimu- 
lus causes  a  greater  single  contraction. 

The  fatigue  curve  of  muscle  excited  to  single  contractions 
repeated  at  a  definite  rate  is  a  straight  line.  The  line  falls 
more  rapidly  with  a  shorter  interval  between  the  stimuli.  The 
effect  of  rest  is  to  increase  the  height  of  the  succeeding  con- 
traction, but  the  contractions  soon  regain  their  position  on  the 
fatigue  curve. 


—26— 

Practical  illustrations  of  the  fatigue  law. 

The  waste  products  of  contraction  diminish  the  irritability 
and  contractility  of  the  muscle.  A  blood  free  muscle  exhausted 
by  stimulation  may  be  made  to  contract  again  after  washing 
out  with  dilute  salt  solution. 

The  work  done  by  a  contracting  muscle  is  measured  by  the 
load  x  height  of  lift.  The  work  done  increases  with  the  load 
to  a  certain  extent  and  then  diminishes  as  the  load  becomes 
greater. 

The  lift  power  of  a  muscle  increases  with  its  thickness,  or 
the  number  of  fibres  side  by  side.  The  extent  of  the  shorten- 
ing increases  with  the  length  of  the  fibres. 

The  maximum  lift  power  for  frog's  muscle  is  2800-3000 
grammes  per  square  cm.  of  cross  section  ;  for  the  human  muscle 
it  is  estimated  to  be  6000-8000  grms. 

PHYSIOLOGICAL  TETANUS. 

When  one  contraction  succeeds  another  in  a  muscle  before 
the  first  is  finished,  the  result  is  a  longer  and  more  extensive 
contraction  or  tetanus.  The  tetanus  is  smooth  when  each 
contraction  begins  during  the  ascending  phase  of  the  preceding 
one.  The  tetanus  is  vibratory  when  the  muscle  has  time  to 
relax  from  one  contraction  before  another  engages  it. 

Distinction  between  physiological  and  pathological  tetanus. 

Proof  of  the  formation  of  tetanus  by  the  summation  of 
single  contractions. 

A  tetanus  may  be  sub-maximal  or  maximal  in  extent. 

A  muscle  may  be  shortened  hj  tetanus  to  one-third  its 
original  length. 

In  tetanus  the  duration,  the  amplitude,  and  the  power  of 
the  contraction  may  be  made  greater  than  by  the  use  of  a 
single  stimulus. 

The  natural  contractions  of  the  living  body  are  sub-maxi- 
mal and  tetanic  in  character. 

The  motor  nerves  cell  is  the  source  of  the  physiological 
stimulus.  Fatigue  and  exhaustion  are  probably  not  so  much 
phenomena  of  nerve  and  muscle  as  of  the  nerve  cell. 

Proofs  of  the  foregoing  statement:  comparison  of  the 
power  of  voluntary  and  artificially  excited  contractions.    The 


—27— 

duration  of  the  shortest  voluntary  contraction  compared  with 
that  excited  by  a  single  artificial  stimulation.  The  muscle 
note  and  its  pitch. 

Voluntary  contractions  are  probably  due  not  to  the  simul- 
taneous, but  to  the  successive  stimulation  of  the  different  fibres 
of  a  muscle. 

Free  circulation  of  blood  in  the  muscle  is  necessary  to  vol- 
untary contraction. 

THE  ELECTRICAL  PHENOMENA  OF  ACTIVE  MUSCLE. 

The  ;"  natural  muscle  current.""  "  current  of  rest."  or  "  de- 
markation  current." 

The  "  negative  variation"  of  the  ;"  demarkation  current.'5 

When  a  muscle  is  stimulated,  the  part  excited  becomes 
electro-negative  to  the  resting  parts. 

The  electric  change  is  due  to  the  chemical  changes  of  the 
active  molecules. 

The  chemical  change  set  up  in  the  muscle  by  stimulation 
is  conducted  along  the  fibres,  and  the  electro-negative  condi- 
tion accompanies  it. 

The  rate  of  this  progression  in  the  frog's  muscle  is  about 
three  metres  per  second.  It  has  already  finished  its  course 
during  the  latent  period  of  stimulation. 

If  an  electric  conductor  be  made  to  connect  the  excited 
electro-negative  part  of  the  muscle  with  its  resting  electro- 
positive part,  a  current  of  electricity  will  flow  through  the 
conductor.  This  current  is  called  the  "  action  current "  of  the 
muscle. 

The  physiological  action  current  is  not  to  be  confused  with 
the  electrical  current  which  is  used  as  a  stimulus. 

Experiment  of  the  ,;  rheoscopic  frog.*'  The  secondary 
muscle  is  thrown  into  tetanus  when  the  primary  muscle  is 
tetanised,  thus  proving  the  interrupted  nature  of  the  electric 
changes  in  the  latter. 

When  the  vital  continuity  of  the  nerve  supplying  the  first 
muscle  is  broken  by  tying  a  string  around  it.  the  tetanus  fails 
in  both  muscles. 

An  action  current  is  set  up  in  a  muscle  by  any  stimulus, 
electrical  or  otherwise. 
4 


—28— 

The  secondary  contraction  of  a  frog's  nerve-muscle  prepar- 
ation caused  by  the  beat  of  the  mammalian  heart. 

COMPARISON  OF  THE  PHYSICAL  AND  CHEMICAL  CHAR- 
ACTERS OF  LIVING  AND  DEAD  MUSCLES. 

Living  resting  muscle  is  soft,  glistening,  elastic,  semi-trans- 
parent and  alkaline  or  amphichroic  in  reaction. 

Living  working  muscle  is  less  elastic,  but  more  extensible 
and  becomes  acid  in  reaction. 

Dead  muscle  is  dull,  opaque,  inelastic  and  is  acid  in  reac- 
tion. 

A  dying  muscle  loses  gradually  its  irritability,  and  then 
goes  rather  suddenly  into  rigor  mortis.  Rigor  is  attended  by 
a  considerable  production  of  sarcolatic  and  carbonic  acids,  by 
a  rise  in  temperature,  and  by  a  shortening  of  the  muscle.  The 
shortening  is  not  powerful ;  limbs  remain  in  about  the  same 
position  as  at  death. 

The  fluctuation  in  length  of  a  muscle  in  rigor. 

Rigor  passes  off  as  decomposition  sets  in. 

THE  CHEMICAL  CHANGES  OF  WORKING  MUSCLE. 

The  excised  muscle  gives  off  no  oxygen  under  the  air 
pump,  but  when  made  to  contract  it  develops  sarcolactic  and 
carbonic  acids  in  an  oxygen  free  atmosphere. 

The  living  muscle  in  the  body  consumes  more  oxygen,  and 
produces  more  carbonic  acid  in  the  active  than  in  the  resting 
condition. 

The  weight  of  muscle  substance  soluble  in  water  decreases, 
while  that  soluble  in  alcohol  increases  in  the  active  as  com- 
pared with  the  resting  condition. 

The  amount  of  acid  produced  by  tetanising  an  excised 
muscle  is  substracted  from  the  amount  finally  produced  by 
the  death  of  the  muscle. 

The  living  muscle  molecule  probably  consists  of  an  essen- 
tial nitrogenous  part  capable  of  building  on  to  itself  certain 
carbon  compounds  by  whose  oxidation  the  energy  of  contrac- 
tion is  produced. 

Every  contraction  is  attended  by  an  evolution  of  heat. 

Comparison  of  the  muscle  with  the  steam-engine. 


—29— 

THE  CHEMISTRY  OF  LIVING  MUSCLE. 

The  contents  of  the  living  muscle  fibre  are  chiefly  semi- 
fluid in  consistency.    This  matter  is  the  muscle  plasma. 

The  artificial  preparation  of  muscle  plasma. 

The  clotting  of  muscle  plasma  and  its  separation  into  clot 
and  serum. 

The  muscle  clot  is  myosin  ;  its  formation  in  dead  muscle 
causes  rigor  mortis. 

The  clot  of  myosin  is  granular ;  its  formation  is  accompa- 
nied by  the  development  of  acid. 

THE  CHEMISTRY  OF  DEAD  MUSCLE. 

The  dead  muscle  contains  seventy-five  per  cent,  water.  Its 
dry  substance  contains  : — 

Proteids:  myosin;  serum-albumin. 

Extractives :  kreatin ;  sarcolactic  acid ;  xanthin ;  hypoxan- 
thin;  uric  acid;  inosit  (in  the  heart) ;  inosinic  acid;  sugar. 

No  urea. 

Fats  in  quantity. 

In  living  muscle  there  is  glycogen  which  is  changed  to 
sugar  on  death.  The  nitrogenous  extractives  are  products  of 
the  chemical  changes  of  the  muscle  substance.  Myosin  does 
not  exist  in  living  muscle. 

THE  PHYSIOLOGY  OF  UNSTRIATED  MUSCLE. 

Unstriated  muscle  is  not  found  unmixed  with  other  tissues 
of  the  body. 

Organs  containing  unstriated  muscle  have  to  some  extent 
power  of  automatic  contraction,  which  may  be  due  to  con- 
tained nervous  elements. 

The  contraction  progresses  slowly  in  a  wave  form  from 
the  spot  stimulated,  and  is  preceded  by  a  long  latent  period. 

In  striated  muscle  the  contraction  wave  passes  only  length- 
wise throughout  the  fibre  ;  in  unstriated  muscle  the  wave  may 
pass  both  in  the  direction  of  the  length  and  the  breadth  of  the 
cell. 

The  impulse  to  contraction  may  probably  be  communicated 
directly  by  one  muscle  cell  to  another  without  the  intervention 
of  nerves. 


—30— 

Unstriated  muscle  is  more  readily  stimulated  by  the  make 
and  break  of  a  galvanic  current  than  by  induction  currents.  A 
succession  of  shocks  produces  a  series  of  increasing  contractions. 

Consider  the  action  of  unstriated  muscle  as  seen  in  the 
peristaltic  action  of  the  intestine  and  ureter  and  in  the  con- 
traction of  the  urinary  bladder. 

The  rheoscopic  frog ;  secondary  tetanus. 

Secondary  contraction  of  frog's  muscle  from  the  beat  of 
the  mammalian  heart. 

Formation  of  acid  with  the  death  of  the  muscle. 


VII.   NERVOUS  TISSUES. 

The  nervous  tissues  consist  of  the  nerves  and  of  the  per- 
ipheral and  central  irritable  non  contractile  organs  in  which 
they  end. 

THE  MINUTE  STRUCTURE  OF  NERVES. 

Nerve  fibres  are  bound  together  in  bundles,  the  funiculi. 

Each  funiculus  is  inclosed  in  several  sheets  of  membrane, 
the  neurilemma.  Each  nerve  is  composed  of  many  funiculi 
inclosed  in  a  common  sheath. 

The  lymph  channels  of  nerves. 

Nerve  fibres  fall  into  two  groups:  (1)  Medullated  or  white 
nerve  fibres.  (2)  Non-medullated,  gray  or  sympathetic  nerve 
fibres. 

Histology  of  the  medullated  fibre ;  the  primitive  sheath ; 
the  medullary  sheath  or  white  substance ;  the  axis  cylinder ; 
the  neuro- keratin  frame-work;  the  nodes  of  Ranvier ;  the 
cement  substance. 

Significance  of  the  nodes  in  the  nutrition  of  the  nerve. 

The  medullary  sheath  is  chiefly  fat,  and  is  not  visibly  differ- 
entiated in  perfectly  fresh  nerve. 

The  axis  cylinder  is  protoplasmic  and  is  the  conductor  of 
the  nervous  impulse. 

Nerves  lose  their  medullary  sheath  before  reaching  their 
peripheral  and  central  terminations. 

The  ending  of  nerves  in  voluntary  muscle ;  ending  in 
involuntary  muscle. 

Histology  of  gray  nerve  fibre;  absence  of  medullary 
sheath ;  nuclei  found  in  the  substance  of  the  fibre. 

The  physiology  of  gray  nerve  fibre. 

In  general,  the  gray  nerve  fibres  arise  from  the  sympathetic 
system  and  are  distributed  to  organs  whose  function  does  not 
involve  consciousness. 

Nerves  of  the  sympathetic  system  leave  the  spinal  cord  as 


—32— 

medullated  fibres  of  much  smaller  calibre  than  those  of  the 
sensory-motor  system.  The  medullary  sheath  of  the  sympa- 
thetic nerve  is  lost  in  its  passage  through  one  or  the  other  four 
chains  of  sympathetic  ganglia.     (Gaskell.) 

CLASSIFICATION  OF  NERVES  ACCORDING  TO  THEIR 
FUNCTIONS.    ( MARTIN. ) 

Sensory. 
Reflex. 
Afferent.  {  Excito-motor. 
j  Vaso  motor. 
^  Inhibitory. 
Peripheral  Nerves. 

f  Motor. 
Vaso-motor. 
Efferent.  <j  Secretory. 
Trophic? 
[  Inhibitory. 

Exciting. 
Intercentral  Nerves.  \  Inhibitory. 

Commissural. 

PHYSIOLOGY  OF  NERVES. 

The  nerve  has  not  automaticity,  but  possesses  to  a  high 
degree  irritability  and  conductivity. 

The  nerve  is  excited  only  by  the  change  of  intensity  of  a 
stimulus. 

The  nerve  is  excited  by  a  much  weaker  induction  shock 
than  is  the  muscle. 

Various  nerve  stimuli ;  mechanical ;  chemical ;  electrical. 

Sensory  and  motor  nerves  show  no  difference  in  their 
structure.  The  nature  of  the  impulse  conducted  by  them  is 
probably  the  same  for  all  kinds  of  stimuli. 

The  change  started  by  an  artificial  stimulation  travels  as  a 
nervous  impulse  along  the  nerve  in  both  directions. 

As  in  the  muscle,  the  excited  parts  of  the  nerve  are  electro- 
negative to  the  resting  parts.  The  action  current  and  the 
change  causing  it  travel  along  the  nerve  of  the  frog  at  the 
rate  of  about  twenty-eight  metres  per  second,  and  of  man 
thirty-three  metres  per  second. 

The  irritability  of  the  nerve  and  its  rate  of  conduction  in- 


—33— 

crease  with  the  temperature.  The  greater  irritability  of  the 
nerve  near  its  cut  end. 

The  energy  of  the  nervous  impulse  is  small  in  amount. 
No  heat  can  be  shown  to  be  evolved,  and  no  chemical  change 
to  take  place  as  a  result  of  nervous  activity. 

All  the  phenomena  of  muscular  contraction  obtained  by 
the  direct  stimulatian  of  the  muscle  substance  may  be  obtained 
by  its  indirect  stimulation  through  the  nerve. 

The  degeneration  and  regeneration  of  cut  nerves. 

ELECTROTONUS. 

When  a  motor  nerve  is.  subjected  to  the  passage  of  a  con- 
stant current  of  electricity  the  muscle  supplied  by  it  contracts 
only  at  the  make  and  break  of  the  current  in  the  nerve,  and 
remains  at  the  rest  during  the  passage  of  the  current. 

The  passage  of  a  galvanic  current  modifies  the  irritability 
and  conductivity  of  the  nerve. 

The  irritability  and  conductivity  of  the  nerve  are  dimin- 
ished in  the  neighborhood  of  the  anode,  and  increased  in  that 
of  the  kathode  of  the  constant  current. 

In  the  region  of  diminished  irritability  the  nerve  is  said  to 
be  in  the  state  of  anelectrotonus.  In  the  area  of  exalted  irrit- 
ability the  nerve  is  said  to  be  in  kathelectrotonus. 

The  electrotonic  conditions  are  more  marked  the  stronger 
the  galvanic  current  used. 

Proofs  of  the  electrotonic  modifications  of  irritability  as 
exhibited  on  the  excised  nerve-muscle  of  the  frog,  and  on  the 
human  arm. 

Application  of  the  principles  of  electrotonus  to  electro- 
therapeutics. 

The  tissue  is  stimulated  at  the  kathode  at  the  make  and  at 
the  anode  at  the  break  of  the  current.  The  onset  of  kathelec- 
trotonus is  a  stronger  stimulus  than  the  disappearance  of  ane- 
lectrotonus, for  the  same  galvanic  current. 

The  "  law  of  contraction  "  and  its  meaning. 


VIII.   REFLEX  ACTION  AND  THE  MECHANISMS  INVOLVED  IN  IT. 

The  origin  of  nerves  from  nerve  cells. 

Various  forms  of  ganglion  cells.  Nerve  cells  in  sporadic 
ganglia ;  in  the  spinal  cord ;  in  the  cerebellum ;  in  the  cere- 
brum. 

In  the  living  body  every  contraction  of  the  skeletal  mus- 
cles is  due  to  stimuli  proceeding  from  nerve  cells. 

NATURE  OF  THE  CONTENTIONS  PRODUCED  BY  THE 
DIRECT  STIMULATION  OF  THE  NERVE  CELLS. 

Make  one  cut  across  a  motor  nerve  and  the  muscle  sup- 
plied by  it  contracts  but  once. 

Cut  across  the  spinal  cord  of  a  frog  and  its  muscles  are 
thrown  into  tetanus. 

The  tetanus  involves  only  the  flexor  muscles  if  the  section 
be  made  across  the  anterior  part  of  the  cord.  Only  the  exten- 
sor muscles  are  contracted  if  the  section  severs  the  posterior 
part  of  the  cord. 

The  experiment  indicates  that  a  nerve  cell  when  artificially 
excited  may  contiiiue  to  send  out  discharges  after  cessation  of 
the  stimulation.  Also  that  there  is  localization  of  motor  func- 
tion in  the  spinal  cord. 

REFLEX  ACTION. 

Nerve  cells  communicate  with  the  exterior  by  means  of 
afferent  nerve  fibres  which  sometimes  terminate  in  modified  end 
organs. 

External  phenomena  excite  afferent  nerves  through  the 
medium  of  sense  organs  in  which  those  nerves  terminate 
peripherally. 

The  nervous  organs  in  which  nerves  terminate  are  excited 
only  by  a  change  in  the  intensity  of  a  stimulus.     The  fineness 
of  the  sense  of  motion  on  the  skin  or  on  the  retina. 
5 


—36— 

Examples  of  sense  organs;  the  retina ;  the  organ  of  Corti; 
tactile  corpuscles. 

The  reflex  action  obtained  by  dipping  the  toe  of  a  headless 
frog  into  dilute  acid. 

Characters  of  the  reflex.  The  latent  period  or  reflex  time. 
The  apparently  purposeful  character  of  the  reflex  in  removing 
irritating  substances. 

Two  general  purposes  of  reflex  action.  1. — Protective. 
2.— Nutritive. 

Purposeful  character  of  a  reflex  as  shown  in  sneezing  and 
coughing. 

The  kind  of  reflex  action  illustrated  in  the  secretion  of 
saliva. 

A  single  stimulus  with  difficulty  provokes  a  reflex,  but  a 
succession  of  stimuli  readily  does  so.  Summation  of  stimuli 
in  the  spinal  cord. 

The  summation  of  sensations  in  awaking  from  sleep  or 
reverie.  -The  extraordinary  results  produced  by  continuous 
irritation  arising  from  an  elongated  prepuce;  from  hemor- 
rhoids; from  an  ulcer;  effect  of  tickling  due  to  summation  of 
stimuli. 

Increase  of  strength  of  stimulation  or  increase  of  its  rate 
shortens  reflex  time. 

The  reflex  time  is  the  period  occupied  chiefly  by  processes 
in  the  nerve  cells. 

The  unco-ordinate  nature  of  reflexes  obtained  by  direct 
stimulation  of  the  afferent  nerve. 

The  value  of  the  peripheral  nervous  organ  in  reflex  action. 
Each  sense  organ  is  differentiated  to  be  specially  irritable  to- 
ward one  certain  form  of  energy. 

Radiation  of  nervous  impulses  in  the  cord. 

Modification  of  irritability  and  conductivity  of  nervous 
centres  in  different  physiological  conditions  and  under  the 
action  of  drugs. 

The  purposeful  character  of  reflex  actions  explained  not  by 
consciousness  of  the  cord  but  by  the  choice  of  paths  of  least 
resistance  which  determine  the  direction  taken  in  the  cord  by 
impulses  arising  from  any  quarter. 

Any  segment  of  the  spinal  cord  may  act  as  a  reflex  centre. 


—37— 

Transferred  pains  and  sympathetic  sensations.  The  "  re- 
flex cough."    Sneeze  provoked  by  a  strong  light. 

The  physiology  of  "  counter-irritation." 

The  typical  mechanisms  employed  in  a  normal  reflex  action 
are:  A  peripheral  organ  for  the  reception  of  the  stimulus  ;  an 
afferent  nerve  fibre,  a  single  nerve  cell  or  a  sensory  and  a 
motor  cell,  an  efferent  nerve  fibre,  a  peripheral  motor  or 
glandular  organ. 

The  essential  characters  of  a  reflex  action  are.  (1)  Its 
unconsciousness ;  (2)  the  want  of  likeness  between  the  effects 
produced  and  the  nature  and  method  of  the  stimulation  em- 
ployed ;  (3)  the  usually  co-ordinated  nature  of  the  action  ; 
(4)  its  involuntary  character. 

The  most  rapid  action  of  which  the  central  nervous  system 
is  capable  is  manifested  in  reflexes. 

Reflex  actions,  as  such,  are  adapted  to  the  protection  of  the 
body  against  accidents,  and  are  also  continually  employed  in 
the  organic  processes  of  the  body. 

Modification  of  the  conductivity  of  the  spinal  cord  in 
strychnia  poisoning. 

INHIBITION. 

The  activity  of  a  nervous  centre  is  the  resultant  of  two 
forces,  one  exciting  to  discharge  and  the  other  resisting  dis- 
charge. Forces  resisting  or  depressing  activity  are  termed 
Inhibitory. 

Examples  of  inhibition :  sneeze  prevented  by  pressure  on 
the  upper  lip ;  trial  of  criminals  by  the  "  rice  ordeal ;  "  stop- 
page of  heart-beat  by  a  blow  on  the  abdomen. 

The  resistance  to  the  action  of  any  nerve  cell  seems  to  be 
increased  by  its  association  with  the  nerve  cells  in  physiolo- 
gical connection  with  it. 

Inhibitory  influences  may  reach  an  active  nerve  cell  from 
any  quarter,  as  along  any  afferent  nerve.  Inhibition  both  from 
within  and  from  without  the  body. 

Inhibition  is  a  regulating  force. 

Consider  the  inhibition  of  a  reflex  action  through  the 
strong  stimulation  of  an  afferent  nerve. 

There  appear  to  be  in  the  brain  special  inhibitory  centres 


—38— 

whose  business  it  is  to  send  out  impulses  to  retard  or  depress 
the  activities  of  the  body.    Centres  of  Setchenow. 

Consider  the  inhibitory  effect  upon  reflex  action  in  the 
frog  of  stimulation  of  the  optic  lobes.  The  inhibition  of  the 
beat  of  the  heart. 

The  general  function  of  inhibitory  centres  is  to  control  and 
make  more  effective  the  activities  of  motor  centres. 

Keflex  time  is  the  period  occupied  by  a  stimulus  in  over- 
coming the  resistance  to  discharge  offered  by  the  nerve  cell. 

Gaskell's  theory  that  motor  nerves  are  katabolic,  destruc- 
tive or  disassimilative  in  their  action  on  tissues,  while  inhibi- 
tory nerves  are  anabolic,  constructive  or  assimilative. 

The  physiological  relation  of  reflex  and  voluntary  actions. 

Cerebral  time. 

The  tendon  reflex.  Modification  of  the  tendon  reflex  by 
the  physiological  condition  of  the  nerve  centres  and  of  the 
peripheral  muscles.    Its  pathological  variation. 

Muscular  tone. 

There  is  no  proof  that  the  sporadic  ganglia  of  the  body 
can  serve  as  reflex  centres.  * 

The  four  groups  of  sympathetic  ganglionic  chains. 

Functions  of  the  sympathetic  or  sporadic  ganglia;  (1)  they 
are  the  seats  of  conversion  of  medullated  into  non-medullated 
nerve  fibres;  (2)  they  exercise  a  nutritive  influence  over  the 
tissues  to  which  their  nerves  are  supplied  ;  (3)  they  are  stations 
for  the  increase  in  number  of  nerve  fibres,  more  fibres  depart 
from  than  enter  them.    They  thus  may  serve  as  "  relay  stations." 

The  physiological  afferent  and  efferent  nerve  fibres  are 
mixed  together  in  the  nerve  trunks,  but  before  reaching  the 
spinal  cord  the  sensory  and  motor  fibres  separate,  the  former 
joining  the  cord  by  the  posterior  spinal  roots,  and  the  latter  by 
the  anterior  roots. 


IX,   THE  CIRCULATION  OF  THE  BLOOD,  AND  THE  ORGANS  OF 

CIRCULATION. 

THE   ANATOMY  AND   HISTOLOGY  OF  THE  MAMMA- 
LIAN HEART. 

The  pericardium ;  its  shape,  dimensions,  and  manner  of 
attachment  to  the  heart  and  chest  wall. 

The  pericardial  fluid. 

The  division  of  the  heart  cavity  into  four  distinct  chambers, 
those  of  the  two  auricles  and  the  two  ventricles. 

The  marked  difference  in  thickness  between  the  walls  of 
the  auricles  and  ventricles.  The  difference  between  the  walls 
of  the  right  and  left  ventricle. 

An  inner  layer  of  muscle  is  pecular  to  each  auricle,  and  an 
outer  layer  is  common  to  both. 

The  spiral  arrangement  of  the  ventricular  muscle  fibres. 

The  comparative  volume  of  the  auricle  when  collapsed  and 
when  distended.     The  auricular  appendage. 

Compare  the  relative  size  of  the  four  chambers  of  the 
empty  heart. 

Notice  the  size,  shape,  and  manner  of  attachment  of  the 
mitral  and  tricuspid  valves.  The  muscle  fibres  upon  the  upper 
surface  of  the  valves.  The  papillary  muscles  and  the  chordce 
tendinece. 

The  columnce  carnew. 

Notice  the  form  and  structure  of  the  vessels  springing  from 
the  heart. 

Notice  the  shape,  structure,  and  manner  of  attachment  of 
the  semilunar  valves. 

Notice  the  shape  of  the  aorta  at  its  base,  and  the  position 
of  the  openings  of  the  two  coronary  arteries. 

Observe  the  fibrous  rings  surrounding  the  auriculo-ventri- 
cular  and  arterial  orifices. 


—40— 

Notice  the  muscle  fibres  continuing  from  the  heart  upon 
the  surface  of  its  great  veins. 

The  endocardium. 

The  histological  characters  of  the  heart  muscle.  The  mus- 
cle is  made  up  of  striated,  nucleated  cells  not  enclosed  in  sar- 
colemma. 

The  intrinsic  ganglia  of  the  heart. 

The  extra-cardiac  nerves: — (1)  Fibres  from  the  vagus 
nerve,  including  physiological  efferent  cardio  inhibitory  and 
physiological  afferent  "depressor  "  fibres.  (2)  Fibres  from  the 
spinal  cord  by  way  of  sympathetic  ganglia,  including  physio- 
logical efferent  "  accelerator  "  fibres. 

THE  STRUCTURE  OF  THE  BLOOD  VESSELS. 

Tunica  adventitia  of  the  arteries. 

The  thick  arterial  wall  and  open  lumen  of  the  empty  vessel. 

The  thin  walled  veins,  collapsing  when  empty. 

Mmute  structure  of  a  small  artery  :— The  lining  epithelium. 
The  thickness  of  the  wall  composed  of  three  distinct  coats : 
(1)  a  narrow  internal  coat  composed  chiefly  of  white  fibrous 
connective  tissue;  (2)  a  thicker  middle  coat  of  circularly  ar- 
ranged unstriped  muscle;  (3)  an  outer  less  firm  coat  composed 
of  mixed  yellow  elastic  and  white  fibrous  tissue. 

In  the  larger  arteries  the  constituents  of  the  three  coats 
intermingle,  while  in  the  arterioles  the  coats  are  sharply 
defined  one  from  the  other. 

The  muscular  element  becomes  proportionately  more  prom- 
inent as  we  proceed  from  the  larger  to  the  smaller  arteries. 

The  capillaries,  composed  entirely  of  the  vascular  endothe- 
lium cells  joined  edge  to  edge. 

The  structure  of  the  veins  corresponds  in  general  with  that 
of  the  arteries,  except  that  the  layer  of  muscle  is  not  so  well 
defined  nor  relatively  so  thick. 

The  valves  in  the  veins. 

Compare  the  elasticity  of  the  artery  with  that  of  the  vein. 

The  artery  is  very  elastic,  its  walls  thick  and  strong.  Curve 
of  elasticity  of  the  arterial  wall.  The  vein  is  more  extensible 
than  the  artery,  and  may  bear  a  greater  hydrostatic  pressure 
without  being  ruptured. 


—41— 

THE  PHYSIOLOGY  Of  THE  HEART. 
THE  AURICULO-VENTRICULAR  VALVES. 

Notice  that  the  surface  of  the  valves  is  considerably  greater 
than  is  necessary  to  separate  completely  the  cavity  of  the 
auricle  from  that  of  the  ventricle  on  each  side  of  the  heart. 

Notice  that  the  chordce  tendinece  are  attached  externally 
not  directly  to  the  heart  wail,  but  through  the  medium  of  the 
papillary  muscles.  The  function  of  these  muscles  in  keeping 
their  tendons  tense  as  the  heart  cavity  becomes  smaller  in  con- 
traction. 

The  inner  ends  of  chordce  springing  from  each  papillary 
muscle  are  attached  to  the  edges,  not  of  a  single  valve,  but  to 
those  of  two  adjacent  ones. 

The  auriculo-ventricular  valves  are  attached  at  their  outer 
edges  to  fibrous  rings  in  the  heart-wall. 

The  use  of  the  muscle  fibres  upon  the  upper  surface  of 
each  valve. 

The  floating  upward  of  the  auriculo-ventricular  valves  dur- 
ing the  pause  of  the  ventricle. 

The  function  of  the  auricle  in  completely  closing  by  its 
contraction  the  auriculo-ventricular  valves. 

The  manner  of  action  of  the  semilunar  valves. 

THE    FUNCTION  AND  COMPARATIVE    PHYSIOLOGY 
OF  THE  HEART. 

The  heart  acts  simply  as  a  pump  whose  valves  enable  it  to 
send  fluid  around  a  continuous  circuit. 

The  respective  functions  of  auricles  and  ventricles. 

Diagrams  illustrating  the  action  of  simple  and  complex 
pumps. 

The  object  of  the  circulation  is  to  bring  new  material  to 
the  tissues  and  remove  waste  matters  from  them. 

The  mammalian  heart  is  a  double  pump  ;  one-half  of  which 
forces  out  venous  blood  and  the  other  half  arterial  blood.  The 
use  to  the  animal  of  this  complex  form  of  the  mammalian 
heart. 

Demonstration  of  the  movement  of  fluid  in  the  sheep's 
heart. 


—42— 

The  co-ordination  throughout  the  animal  kingdom  of  the 
anatomical  structure  of  the  heart  with  the  physiological  needs 
of  the  organism. — The  contractile  circulatory  apparatus  of  the 
amceba  ;  of  a  worm  ;  of  a  snail  ;  of  a  frog. 

THE     PHENOMENA    INVOLVED    IN    THE    CARDIAC 

CYCLE. 

The  beat  of  the  excised  heart  of  the  frog.  The  active  sys- 
tole and  the  passive  diastole.  The  rounder  base  and  shorter 
long  axis  of  the  heart  in  systole. 

The  wall  of  the  ventricle  becomes  tense  and  hard  in  sys- 
tole. 

The  position  of  the  mammalian  heart  in  the  living  body; 
the  change  of  position  on  opening  the  chest  wall. 

The  movements  of  the  living  heart  within  the  chest : — The 
slight  rotation  round  the  long  axis.  The  marked  movement 
of  base  toward  the  apex,  and  its  cause.  Effect  upon  the  posi- 
tion of  the  heart  and  on  the  movement  of  its  base,  of  bleed- 
ing.   The  absence  of  locomotion  in  the  apex. 

In  the  erect  position  of  the  body  the  apex  of  the  heart 
probably  persistently  touches  the  chest  wall,  and  the  cardiac 
impulse  is  due  to  the  hardening  of  the  ventricle  in  systole. 

The  phases  of  the  cardiac  cycle  : — The  duration  of  the  auri- 
cukr  systole  and  the  condition  of  the  rest  of  the  heart  during 
it.  The  duration  of  the  ventricular  systole  and  the  condition 
of  the  rest  of  the  heart  during  it.  The  duration  of  common 
diastole  of  the  heart.    The  length  of  the  whole  cardiac  cycle. 

Time  JRelatious  of  the  Phases  of  the  Cardiac  Cycle:    (Foster's   Physi- 
ology.) 

Seconds. 

Systole    of    ventricles   previous  to  opening    of   the    semilunar 

valves 0.085 

Escape  of  blood  into  the  aorta 0.100 

Continued  contraction  of  emptied  ventricles 0.115 

Total  systole  of  ventricles 0.3 

Diastole  of  both  auricles  and  ventricles,  or  common  diastole 0.4 

Systole  of  auricles 0.1 

Sum  of  the  two  (pause  between  2d  and  1st  sounds) 0.5 

Total  cardiac  cycle '. 0.8 


—43— 

The  nature  and  time  relations  of  the  changes  going  on 
within  the  various  chambers  of  the  heart  throughout  the  car- 
diac cycle.    The  experiments  of  Chauveau  and  Marey. 

The  cardiac  systole  begins  in  the  great  veins. 

The  quick  peristaltic  contraction  of  the  auricles. 

The  long  persistence  ot  the  phase  of  extreme  contraction 
in  the  ventricles. 

The  ventricles  probably  empty  themselves  completely  at 
each  systole.    The  auricles  never  do. 

The  u  cardio-pneumatic  "  movements. 

THE  WORK  DONE  BY  THE  HEART. 

Factors  which  determine  the  amount  of  work  done  by  the 
heart: — (1)  The  amount  of  blood  pumped  out  at  each  beat; 
(2)  the  resistence  to  be  overcome;  (3)  the  frequency  of  the 
beats. 

Calculation  of  the  amount  of  work  done  by  the  human 
heart  in  24  hours. 

The  work  power  of  the  heart  is  alone  quite  sufficient  to 
cause  the  blood  to  circulate  through  the  whole'body. 

THE  SECONDARY  MECHANICAL  AIDS   TO  THE  WORK  OF 

THE  HEART. 

The  assistance  given  to  the  filling  of  the  auricles  by  the 
movements  of  inspiration. 

The  suction  of  blood  into  the  auricles  due  to  the  move- 
ment of  the  base  of  the  ventricle  when  the  latter  contracts. 

The  help  offered  by  the  coronary  circulation  to  the  filling 
of  the  ventricles. 

The  help  offered  by  the  elasticity  of  the  ventricular  wall 
to  the  filling  of  the  ventricle. 

Negative  pressure  in  the  left  ventricle  at  the  beginning  of 
its  diastole. 

The  circulatory  variations  in  organs  outside  the  heart  as 
shown  by  the  plethysmograph. 

The  movements  of  respiration  are  powerful  aids  to  the 
circulation. 

The  aid  rendered  to  the  filling  of  the  ventricles  by  the 
slipping  of  the  ventricles  over  the  blood  in  the  auricles  in  ven- 
tricular diastole,  due  to  the  aortic  pull. 


—44— 

THE  INFLUENCES  WHICH  INITIATE  AND  MAY  MOD- 
IFY THE  BEAT  OF  THE  HEART. 

The  cardiac  beat  is  an  automatic  action  and  may  be  carried 
on  in  a  normal  manner  by  the  excised  organ. 

The  impulse  to  activity  is  discharged  rhythmically,  probably 
from  certain  nerve  centres  within  the  substance  of  the  heart. 
In  some  animals  the  heart  muscle  itself  has  automatic  contrac- 
tility. 

Theoretical  explanation  of  automatism. 

The  rate  and  nature  of  the  beat  are  profoundly  modified 
by  various  secondary  influences.  The  following  are  the  secon- 
dary influences  which  may  be  shown  to  operate  on  the  heart, 
and  to  their  variation  must  be  due  any  alteration  in  the  charac- 
ter and  rhythm  of  the  automatic  beat : 

1.  The  intra-cardiac  blood  pressure.  The  diastolic  intra- 
cardiac pressure  depends  upon  the  volume  of  blood  which 
flows  into  the  heart,.  The  systolic  intra-cardiac  pressure  de- 
pends upon  the  resistance  to  the  flow  of  blood  from  the  heart, 
or  upon  the  blood  pressure  within  the  aorta  and  pulmonary 
artery. 

2.  The  temperature  of  the  blood  entering  the  heart. 

3.  The  chemical  constitution  of  the  blood  supplying  the 
heart. 

4.  The  efferent  nerves  reaching  the  heart  from  extra- 
cardiac  centres. 

THE    INFLUENCE   UPON    THE   HEART-BEAT    OF    INTRA- 
CARDIAC BLOOD-PRESSURE. 

The  heart  of  the  frog,  cut  from  the  body  and  empty,  beats 
very  feebly  and  comes  to  rest  after  a  while ;  pass  through  its 
cavities  a  weak  saline  solution  under  pressure  and  the  beats 
become  much  stronger  or  go  on  again  for  a  time.  Distension 
of  the  cardiac  wall  is  a  stimulus  to  the  activity  of  the  heart' 
The  effect  is  more  striking  and  lasting  if  blood  instead  of  salt 
solution  be  used. 

When  the  excised  heart  is  normally  beating  with  an  artfi- 
cial  supply  of  blood,  neither  variation  of  arterial  pressure  nor 
variation  of  venous  pressure  produces  any  definite  alteration 


—45— 

in  the  rhythm  of  the  heart-beat.  The  rhythm  of  the  heart- beat 
is  not  directly  afiected  by  changes  of  intra-cardiac  pressure. 

The  work  done  by  the  heart  and  the  force  of  its  beat  in- 
crease with  intra-cardiac  blood-pressure. 

The  normal  heart  is  at  any  moment  able  to  accomplish 
much  more  work  than  it  is  required  to  do. 

INFLUENCE   OF  THE   TEMPERATURE  OF   THE   BLOOD 
ENTERING  THE  HEART. 

The  heart  muscle  is  extremely  susceptible  to  changes  of 
temperature.  The  rhythm  of  the  beat  is  uniformly  quicker 
with  a  higher  and  slower  with  a  lower  temperature.  Changes 
in  the  temperature  of  the  blood  amounting  to  a  fraction  of  a 
degree  alter  the  rhythm  of  the  mammalian  heart-beat. 

INFLUENCE  OF   THE  CHEMICAL  CONSTITUTION  OF  THE 
BLOOD  SUPPLYING  THE  HEART. 

The  heart  is  remarkably  insensitive  to  deterioration  in  the 
nutritive  fluid  supplying  it.  The  action  or  the  frog's  heart 
under  minute  quantities  of  nutritive  material.  The  beat  of  the 
isolated  mamalian  heart  supplied  by  blood  poor  in  oxygen  and 
rich  in  waste  matters. 

But  the  heart  is  very  sensitive  to  the  action  of  certain 
drugs.  Certain  of  these  effect  the  muscle  of  the  heart  directly, 
others  operate  on  various  parts  of  its  intrinsic  nervous  mecha- 
nism. 

The  action  of  alkali  on  the  heart  muscle. 

The  action  of  acid  on  the  heart  muscle. 

The  action  of  di gitalin  on  the  heart  muscle. 

The  action  of  atropin. 

The  action  of  muscarin  and  of  pilocarpin. 

THE  INFLUENCE  OF  EFFERENT  NERYES  REACHING 
THE  HEART  FROM  EXTRA-CARDIAC  CENTRES. 

Modifications  of  the  heart-beat  are  probably  normally 
nearly  altogether  due  to  impulses  proceeding  along  the  heart 
nerves.  The  cardio- inhibitory  nerve: — fibres  arising  from  the 
spinal  accessory  nerve  join  the  pneumogastric  trunk  within  the 
skull  and  are  given  off  from  this  nerve  again  in  the  neighbor- 


—46— 

hood  of  the  heart.  Stimulation  of  the  peripheral  end  of  the 
cut  vagus  causes  slowing  of  the  heart-beat  if  the  stimulation 
be  weak,  stops  the  beat  if  stimulation  be  strong. 

The  inhibition  due  to  stimulation  is  preceded  by  a  latent 
period  of  one  or  two  heart-beats. 

Exhaustion  of  the  inhibitory  fibres ;  after  being  brought 
to  a  standstill,  the  heart  soon  commences  to  beat  again  though 
the  stimulation  be  kept  up. 

Evidence  for  the  constant  action  of  the  vagus  inhibitory 
fibres  upon  the  heart. 

The  vagus  probably  contains  two  other  separate  sets  of 
efferent  fibres  whose  action  in  the  one  case  strengthens,  in  the 
other  causes  weakening  of  the  heart-beat,  without  alteration 
of  its  rhythm.  Evidence  derived  from  the  heart  of  the  frog 
and  terrapin. 

The  cardiac  accelerator  fibres  arise  from  the  spinal  cord  and 
reach  the  heart  through  the  last  cervical  and  first  thoracic  sym- 
pathetic ganglia. 

The  motor  augmentor  and  accelerator  fibres  probably  have 
their  origin  with  the  sympathetic  system,  while  the  inhibitory 
fibres  arise  from  the  vagus  centre. 

Effect  of  stimulating  the  peripheral  end  of  the  spinal  cord 
divided  in  the  neck,  or  the  peripheral  ends  of  the  divided 
accelerator  fibres. 

The  heart-beat  is  quickend  by  the  stimulation.  The  stim- 
ulus required  is  much  stronger  than  for  the  inhibitory  nerve. 
The  latent  period  is  long,  and  the  effect  of  1he  stimulation  per- 
sists for  some  time  aftes  the  cessation  of  the  latter. 

When  the  cardio- inhibitory  and  the  accelerator  fibres  are 
simultaneously  stimulated,  the  heart  is  brought  to  a  stand  still 
as  if  the  vagus  alone  were  irritated. 

PHYSIOLOGICAL  CONDITIONS  WHICH  MODIFY  THE 
HEART-BEAT. 

Emotions  may  operate  on  the  extra-cardiac  heart  centres  so 
as  to  cause  a  change  in  both  rate  and  character  of  heart-beat. 

Increase  of  blood-pressure  in  the  brain  stimulates  the  car- 
dio-inhibitory  centres  directly. 

Increase  of  general  arterial  blood-pressure  probably  slows 


—47— 

the  heart-beat  reflexly.  Reflex  slowing  through  stimulation  of 
the  depressor  nerve. 

Reflex  inhibition  may  occur  through  the  stimulation  of  any 
sensory  nerves. 

Diminution  of  blood-pressure  in  the  brain  directly  stimu- 
lates the  cardio  accelerator  centres. 

The  high  blood-pressure  of  chronic  renal  disease  is  accom- 
panied by  an  infrequent,  steady  pulse. 

Acceleration  of  pulse  on  the  exhibition  of  amyl  nitrite. 

Increased  venosity  of  the  blood  stimulates  the  cardio- 
inhibitory  centre. 

The  intimate  reflex  association  between  the  heart  and  the 
digestive  tract. 

THE  AUTOMATICITY  OF  THE  HEART. 

The  phenomena  offered  by  the  frog's  heart  when  it  is  cut 
in  different  directions  and  when  its  various  parts  are  separated 
from  each  other. 

The  graded  automaticity  of  the  different  parts  of  the  heart ; 
the  decline  of  physiological  resistance  to  discharge  from  the 
venous  sinus  to  the  ventricle. 

The  coordination  of  movement  in  different  parts  of  the 
tortoise's  heart  brought  about  by  nerves. 

The  isolated  ventricle  of  the  frog's  heart  does  not  beat 
spontaneously,  but  rhythmic  beats  follow  when  it  is  distended 
with  fluid. 

The  function  of  the  ventricles  is  to  drive  the  blood  respect- 
ively in  its  pulmonary  and  systemic  circulation. 

The  functions  of  the  auricles  are,  by  the  frequency  and 
character  of  their  pulsations,  to  regulate  the  rate  and  character 
of  the  ventricular  contraction.  By  their  beat  to  complete  the 
closure  of  the  auriculo-ventricular  valves ;  to  serve  as  a  store- 
house for  blood  during  ventricular  systole. 

The  law  for  the  contraction  of  cardiac  musele  : — Unlike  the 
skeletal  muscles,  cardiac  muscle  refuses  to  give  sub-maximal 
contractions  on  applying  weaker  stimuli. 

The  heart's  contraction  is  probably  not  a  tetanus,  but  a 
long- continued  single  contraction. 

The  action  current  of  the  heart. 


THE  APEX  BEAT  AND  THE  SOUNDS  OF  THE  HEART. 

The  apex  beat  felt  outside  the  chest  wall  lasts  throughout 
the  systole  of  the  ventricle  and  is  due  to  this.  The  impulse  is 
due,  probably,  not  to  a  blow  of  the  heart's  apex  against  the 
chest  wall,  but  simply  to  the  hardening  of  the  heart  muscle. 

The  topographical  relations  of  heart,  lungs,  chest-wall  and 
diaphragm  in  their  different  phases  of  activity. 

The  normal  place  of  the  apex  beat  and  its  pathological 
variations. 

The  two  sounds  of  the  heart  ;  the  time  of  their  occurrence 
in  the  cardiac  cycle  and  their  difference  of  quality. 

The  first  sound ;  probably  both  muscular  and  valvular  in 
origin. 

The  second  sound ;  due  to  the  snapping-to  of  the  semilunar 
valves. 

Owing  to  difference  between  the  blood-pressures  in  the  two 
vessels,  the  aortic  semilunar  valves  close,  on  the  average,  about 
.05  second  before  those  of  the  pulmonary  artery. 

THE  CIRCULATION  OF  THE  BLOOD. 

Proof  that  the  work  power  of  the  heart  is  sufficient  to  com- 
plete the  circulation  of  the  blood. 

Rate  of  circulation;  the  blood  completes  its  circuit  from 
ventricle  to  ventricle  in  man  in  about  23  seconds. 

The  area  of  the  arterial  vascular  bed  increases  from  the 
heart  to  the  capillaries  and  then  decreases  in  the  veins  to  the 
heart.  The  flow  of  blood  is  slowest  where  it  passes  through  the 
greatest  area,  that  of  the  capillaries.  The  sum  of  the  areas  of 
cross-section  of  the  systematic  capillaries  is  probably  eight 
hundi'ed  times  as  great  as  that  of  the  aorta. 

The  circulation  of  the  blood  as  observed  in  a  frog  under 
the  microscope.  The  comparison  of  the  flow  in  arteries,  capil- 
laries and  veins. 

The  "  axial  "  current ;  the  "  inert  "  layer  ;  the  respective 
movements  of  white  and  red  corpuscles. 

The  importance  to  the  circulation  of  the  preservation  of 
the  normal  ratio  of  the  specific  gravity  of  the  blood  plasma 
to  that  of  the  corpuscles. 


—49— 

The  changes  in  the  circulation  brought  about  by  the  pro- 
cess of  inflammation. 

THE  HYDRAULICS  OF  THE  CIRCULATION. 

The  agents  concerned  in  the  circulation ; — (1)  an  incom- 
pressible fluid ;  (2)  a  pump  of  intermittent  action;  (3)  a  set 
of  elastic  tubes. 

If  an  artery  be  cut  across  there  is  a  continuous  flow  of 
blood  from  its  central  end  with  an  increased  spurt  at  each 
heart-beat.  Cut  across  a  vein  and  there  is  a  steady  flow  of 
blood  without  pulsation  from  its  peripheral  end. 

If  a  mercury  manometer  be  attached  to  an  artery  of  a  liv- 
ing animal  the  position  of  the  mercury  will  show  that  the  blood 
in  the  artery  is  under  considerable  pressure,  the  blood-pressure, 
which  fluctuates  with  each  beat  of  the  heart. 

If  a  manometer  be  attached  to  a  vein  the  mercury  will 
show  a  very  small  blood-pressure  and  no  pulsations. 

Consider  the  causes: — (1)  of  the  high  arterial  and  low 
venous  blood-pressure;  (2)  of  the  continuous  flow  of  blood 
brought  about  by  the  intermittent  action  of  the  pump  ;  of  the 
loss  of  the  pulse  in  the  veins. 

The  law  of  the  fall  of  fluid  pressure  in  a  tube  offering  equal 
resistance  to  flow  in  all  its  parts. 

Volkmamvs  schema. 

Weoer's  schema. 

The  minor  arterial  schema. 

The  major  arterial  schema. 

The  resistance  to  the  movement  of  the  blood  is  internal; 
that  is,  due  to  the  friction  of  the  fluid  particles  against  each 
other.  Conditions  determining  internal  and  external  friction 
in  the  movements  of  fluids. 

The  internal  friction  increases  fast  as  the  calibre  of  the 
vessels  decreases ;  hence  the  chief  resistance  to  the  circulation 
is  in  the  capillaries,  or  is  peripheral. 

Because  of  the  peripheral  resistance  the  arterial  walls  are 
stretched  by  the  blood  pumped  from  the  heart,  and  the  strained 
wall  reacting  on  the  fluid  produces  the  high  arterial  pressure. 

The  arterial  walls  being  kept  constantly  stretched,  they 


—50— 

squeeze  constantly  upon  the  inclosed  fluid ;  hence  the  flow  from 
a  cut  artery  is  continuous 

If  the  heart  stop,  the  circulation  continues  to  go  on  until 
the  arteries  have  come  to  a  condition  in  which  they  are  not 
•stretched. 

The  blood  pressure  is  the  immediate  cause  of  the  circula- 
tion. The  action  of  the  heart  is  its  remote  cause  and  operates 
through  keeping  the  arteries  stretched  by  forcing  into  them 
fresh  quantities  of  fluid. 

The  energy  of  the  blood-pressure  is  used  up  in  overcoming 
resistance  to  the  circulation,  and  as  the  chief  resistance  is 
offered  by  the  capillaries,  there  is  a  sudden  fall  of  pressure  be- 
tween the  arteries  and  the  veins. 

Each  new  quantity  of  fluid  thrown  into  the  base  of  the 
aorta  distends  the  vessel  there,  and  this  distension  runs  along 
the  artery  as  the  pulse  wave. 

The  rate  and  height  of  the  pulse  wave  depend  upon  the 
elastic  qualities  of  the  arterial  wall. 

The  pulse  wave  started  at  any  systole  of  the  heart  travels 
much  faster  than  the  blood  whose  entrance  into  the  aorta 
caused  it. 

The  energy  of  the  pulse- wave  is  used  up  in  stretching  the 
vascular  wall ;  hence  the  height  of  the  wave  decreases  from  the 
heart  outwards,  being  distributed  over  an  increasing  amount  of 
elastic  material.     The  pulse  in  atheroma  of  the  arteries. 

The  varieties  of  pulse  characters.  The  influence  of  the 
heart-beat  and  of  the  arterial  blood-pressure  on  the  character 
of  the  pulse. 

The  effect  on  the  pulse  of: — age  ;  exercise  ;  position  of  the 
body,  sleep;  digestion;  external  temperature;  altitude;  time 
of  day;  individual  traits. 

Primary  and  secondary  pulse- waves. 

Study  of  sphygmographic  tracings. 

The  veins  alone  could  contain  all  the  blood  of  the  body. 
The  arteries  are  overfull. 

THE  USE  OF  ARTERIAL  ELASTICITY. 
A  greater  amount   of  fluid  is  forced  by  an  intermittent 


—51— 

pump  in  a  given  time  through  an  elastic  tube  than  through  a 
rigid  one  of  the  same  calibre. 

The  energy  of  the  heart's  systole  is  stored  in  the  arterial 
wall,  and  acts  throughout  the  cardiac  cycle  as  driving  force  of 
blood.  By  this  means  the  useful  energy  of  the  heart  is  not 
limited  in  time  to  its  systole,  but  is  distributed  through  the 
whole  cardiac  cycle.  Consider  the  analogy  of  many  artificial 
machines.  Consider  the  results  to  the  heart  and  the  circulation 
of  the  arteries  being  rigid  tubes. 


All  the  energy  of  motion  that  is  lost  to  the  blood  in  circu- 
lation reappears  as  heat  and  goes  to  warming  the  tissues. 

As  the  arterial  blood-pressure  is  the  force  which  drives  the 
blood  round  its  circuit,  it  is  of  vital  importance  to  the  animal 
that  a  pretty  constant  mean  pressure  be  maintained. 

MEANS  BY  WHICH  ARE  REGULATED  THE  GENERAL 
BLOOD-PRESSURE  AND  LOCAL  BLOOD-SUPPLY. 

The  factors  which  determine  the  power  of  the  blood-pres- 
sure are  three: — (1)  The  force  and  frequency  of  the  heart-beat 
as  determining  the  quantity  of  blood  pumped  into  the  arteries. 
Other  things  being  equal,  blood-pressure  increases  with  the 
quantity  of  blood  forced  out  of  the  heart  in  a  given  time. 

(2)  The  peripheral  resistance;  arterial  pressure  increases 
and  venous  pressure  proportionately  decreases  as  the  peripheral 
resistance  becomes  greater,  other  factors  remaining  the  same. 

(3)  The  elasticity  of  the  arteries  ;  other  things  remaining 
equal,  blood-pressure  increases  with  increase  of  elasticity,  or 
resistance  to  distension,  of  the  arterial  walls. 

Inhibition  of  the  heart's  action  through  stimulation  of  the 
vagus  nerve  causes  a  sudden  fall  of  blood-pressure. 

THE  VASO-MOTOR  REGULTION  OF  BLOOD  PRESSURE. 

Withdrawal  of  a  large  quantity  of  blood  from  an  animal 
does  not  lower,  except  momentarily,  the  blood-pressure. 

The  injection  of  a  large  quantity  of  foreign  blood  into  the 
vessels  of  an  animal  produces  no  permanent  rise  of  blood- 
pressure. 

7 


—52— 

When  the  spinal  cord  of  an  animal  is  divided  in  the  neck 
the  mean  arterial  blood-pressure  decreases  to  a  small  fraction  of 
its  former  value.  When  the  peripheral  end  of  the  cat  cord  is 
stimulated  arterial  pressure  rises  again.  Both  the  fall  and  the 
rise  of  pressure  are  somewhat  gradual. 

The  vaso-motor  centres  in  the  medulla  oblongata. 

Efferent  impulses  proceed  from  the  vaso-motor  centre 
along  vaso-motor  nerves  to  all  parts  of  the  body,  and  keep  the 
muscular  coats  of  the  small  arteries  and  arterioles  in  a  state  of 
tonic  contraction,  thus  increasing  the  peripheral  resistance  to 
the  flow  of  blood. 

Diminution  of  blood-pressure  in  the  brain  stimulates  the 
vaso  constrictor  centre. 

0  02  in  the  blood  stimulates  the  vaso-constrictor  centre. 

Secondary  vaso-motor  centres  in  parts  of  the  brain  other 
than  the  medulla  oblongata^  and  in  the  spinal  cord. 

It  is  not  proven,  but  is  not  improbable,  that  the  capillaries 
are  under  vaso-motor  control. 

The  vaso-motor  nerves  form  a  part  of  the  sympathetic  ner- 
vous system. 

The  experiment  of  cutting  and  stimulating  the  cord  of  a 
frog  while  its  circulation  is  observed  under  the  microscope. 

THE  REGULATION  OF  LOCAL  BLOOD  SUPPLY. 

The  various  organs  of  the  body  require  an  increase  of 
blood  supply  during  their  periods  of  activity  and  a  lessei 
quantity  in  the  intervals  between. 

Stimulation  of  sympathetic  nerve  branches  supplying  any 
area  nearly  always  produces  contraction  of  the  vessels  in  that 
area. 

Efferent  vaso-dilator  as  distinguished  from  vaso-constrictor 
nerves. 

The  vaso-motor  effect  of  stimulating  the  peripheral  end  of 
the  mylo-hyoid  nerve  in  the  frog. 

The  effect  of  stimulating  the  peripheral  end  of  the  chorda 
tympani  upon  the  circulation  in  the  sub-maxillary  gland  of  the 
dog. 

The  physiology  of  blushing. 


—53— 

The  functional  vase-motor  changes  of  erectile  tissues. 

The  changes  in  the  circulation  of  a  vascular  area  on  stimu- 
lating its  vaso-dilator  nerve:  The  increased  calibre  of  the 
arterioles ;  the  more  rapid  blood  current ;  the  flow  of  red  blood 
through  the  veins ;  the  venous  pulse. 

Dilation  of  an  arteriole  brings  about  an  increase  of  blood 
pressure  in  the  capillaries  springing  from  it  and  hence  an  in- 
crease of  transudation  through  their  walls. 

The  evidence  for  the  presence  in  the  medulla  of  a  double 
vaso-motor  centre,  one  part  sending  out  vaso-constrictor 
nerves,  the  other  part  supplying  vaso-dilator  nerves.  When 
one  organ  receives  more  or  less  blood  than  usual,  there  must 
be  an  alteration  of  vaso-motor  tone  in  the  blood-vessels  of 
other  districts  in  order  that  the  mean  blood-pressure  shall  re- 
main constant. 

The  vaso  motor  tone  of  the  vessels  of  the  lower  limbs  is 
slight  before  rising  in  the  morning.  On  standing  erect  the 
weight  of  the  blood  engorges  the  feet  until  vaso-constriction  in 
those  parts  is  gradually  established. 

Dizziness  on  suddenly  rising  from  a  stooping  posture.  The 
establishment  of  pathological  diminution  of  vaso-motor  tone 
in  the  pleuras,  etc.,  leading  to  local  hypersemia. 

Local  paralysis  of  vaso-motor  mechanism  by  means  of  lig- 
ature or  long  continued  pressure. 

The  influence  of  temperature  and  of  mechanical  disturb- 
ances on  the  vaso-motor  activity  of  the  skin. 

Compensatory  vaso-motor  action,  as  of  the  skin  and  kid- 
neys. 

Gradual  recovery  of  vascular  tone  in  any  area  after  cutting 
off  its  vaso-motor  nerves. 

The  relation  of  the  sympathetic  ganglia  to  vaso-motor  tone. 

THE    KEFLEX    EXCITEMENT    OF  THE   VASO-MOTOR 

CENTRES. 

Stimulation  of  the  central  end  of  nearly  any  sensory  nerve 
produces  general  reflex  vaso-motor  constriction  and  a  conse- 
quent rise  of  blood-pressure  in  a  normal  or  a  curarized  animal, 
but  a  fall  of  pressure  in  an  animal  deeply  narcotised  by 
chloral. 


—54— 

The  function  of  the  depressor  nerve,  which  in  the  cat  and 
rabbit  finds  its  way  to  the  heart  in  a  path  independent  of  the 
vagus.  The  depressor  is  an  afferent  nerve ;  when  divided 
stimulation  of  its  central  end  brings  about  a  fall  of  blood- 
pressure  without  marked  change  in  the  pulse-rate,  provided 
the  vagi  be  cut.  The  fall  of  blood-pressure  is  due  to  reflex 
dilation  of  the  abdominal  vessels. 

The  reflex  dilation  of  the  vessels  in  a  rabbit's  ear  through 
stimulation  of  the  great  auricular  nerve. 

The  reflex  dilation  of  the  blood  vessels  of  glands  due  to 
the  stimulating  effect  of  food  upon  the  appropriate  mucous 
membranes. 

Remembering  that  arterial  pressure  is  the  driving  force  of 
the  blood,  consider  the  difference  of  physiological  effect  be- 
tween rapidly  drawing  a  certain  amount  of  blood  from  an 
artery  and  from  a  vein. 


THE  LYMPHATIC  VESSELS  AND  THE  FLOW  OF  LYMPH. 

Two  modes  of  origin  of  lymphatic  vessels  ;—plexiform 
and  lacunar. 

The  relative  size  and  direction  of  lymph  and  blood  capil- 
laries. 

The  thin,  vein-like  walls  of  lymphatic  vessels ;  their  numer- 
ous valves. 

The  stomata  of  serous  membranes. 

Every  tissue  element  probably  lies  in  a  lymphatic  space 
from  which  fluid  rapidly  reaches  lymphatic  channels. 

The  direction  of  flow  in  the  lymphatic  vessels. 

Influences  modifying  the  flow  of  lymph : — muscular  action ; 
position  of  the  body;  respiratory  movement.  Flow  from  the 
opened  thoracic  duct  of  a  dog. 

The  influence  of  the  respiratory  movements  of  the  dia- 
phragm on  the  flow  of  the  blood  and  the  lymph. 


X,  THE  RESPIRATION, 


THE    RESPIRATORY    MECHANISM    AND    ITS    FUNC- 
TIONS. 

The  object  of  the  respiration  is  the  removal  from  the  body 
of  waste  products  of  tissue  change  and  the  renewal  of  oxygen 
to  the  tissues.  The  lungs  are  both  excretory  and  alimentary  in 
function. 

This  interchange  of  matter  is  brought  about  by  the  process 
of  diifViSion. 

The  function  of  respiratory  movement  is  to  hasten  the  pro- 
cess of  diffusion. 

The  law  for  the  absorption  of  gases  by  liquids. 

The  modification  of  the  respiratory  apparatus  in  different 
animals.  Respiration  in  the  amceba  ;  in  a  marine  worm  ;  in  a 
■fish  ;  in  an  insect ;  in  a  frog  /  in  a  mammal. 

THE    STRUCTURE   OF    THE    RESPIRATORY   ORGANS 

IN  MAN. 

The  trachea  and  bronchi;  the  incomplete  cartilaginous 
rings ;  the  mucous  glands ;  the  ciliated  epithelium. 

The  lungs ;  the  lung  alveoli ;  the  air-cells  and  their  flattened 
lining  epithelium ;  the  capillary  circulation  in  the  lung. 

Comparison  of  the  lungs  of  the  batrachian,  reptile  and 
mammal. 

The  muscular  and  elastic  tissue  of  the  lung. 

The  topographical  relations  of  the  lungs.     The  pleura. 

Functions  of  the  cilia  in  cleansing  the  air  passages  and 
aiding  in  the  mixture  of  gases.  Rapidity  of  this  mixture ;  time 
taken  for  H2  $  injected  into  the  blood  to  reappear  in  the  ex- 
pired air. 

THE  MOVEMENTS  OF  RESPIRATION. 

The  lungs  are  extremely  elastic  and  extensible.    They  are 


—58— 

but  semi-distended  in  the  thorax.  The  pressure  exerted  by  the 
elasticity  of  the  lungs  in  man'  is  about  that  of  a  column  of 
mercury  five  millimetres  high. 

The  atmospheric  pressure  upon  the  inside  of  the  lungs 
keeps  them  distended  while  in  the  closed  chest. 

When  the  chest  cavity  is  enlarged  in  inspiration  the  atmos- 
pheric pressure  causes  the  lungs  to  fill  the  new  space ;  and 
when  the  cavity  becomes  smaller  in  expiration  the  elasticity  of 
the  lung  substance  causes  a  corresponding  diminution  in  the 
bulk  of  the  lungs. 

Demonstration  on  an  artificial  schema  and  on  a  rabbit  of 
the  effects  of  the  respiratory  movements  upon  the  contents  of 
the  chest. 

In  ordinary  breathing  inspiration  only  involves  muscular 
effort,  the  expiration  being  performed  by  the  elastic  reaction 
of  the  parts. 

The  cavity  of  the  chest  is  increased  vertically  by  the  con- 
traction of  the  muscle  of  the  diaphragm.  The  effect  of  violent 
contraction  of  the  diaphragm  upon  the  lower  ribs  and  upon  the 
abdominal  viscera. 

The  lateral  increase  of  the  chest  cavity  due  to  contraction 
of  the  diaphragm. 

The  movements  of  the  ribs  and  sternum  in  respiration. 

The  effect  on  the  size  of  the  chest  cavity  of  the  position  of 
the  spinal  column. 

The  external  intercostals,  the  scaleni  and  the  levatores  cos- 
tarum  are  the  elevators  of  the  ribs  in  ordinary  inspiration. 

Consider  the  adaptation  of  shape  and  position  of  the  ribs 
and  costal  cartilages  to  the  purposes  of  respiration. 

Resistances  to  be  overcome  in  inspiration : — Elastic  tension 
of  lungs ;  the  weight  of  the  movable  parts  of  the  thorax ; 
elasticity  of  costal  cartilages  ;  depression  of  abdominal  viscera ; 
elasticity  of  abdominal  walls. 

In  labored  inspiration  the  following  muscles  are  also  called 
into  play  : — Serratus  magnus,  pectoralis  minor, pector alls  ma- 
jor, latissim.us  dorsi,  serratus  posticus  superior,  serratus  pos- 
ticus inferior,  quadratus  lumborum,  sacro  lumbalis. 

Consider  the  system  of  mechanical  levers  and  fulcra  used 
in  various  grades  of  respiratory  effort.    Two  classes  of  respira- 


—59— 

tory  muscles:  (1)  fixers  of  the  fulcra;  (2)  movers  of  the 
levers. 

The  internal  intercostals  are  probably  muscles  of  ordinary 
expiration. 

In  labored  expiration  the  abdominal  muscles  are  the  chief 
active  agents. 

The  action  of  the  intercostal  muscles  as  illustrated  on  Bam- 
berger's schema. 

In  the  human  species  costal  respiration  is  relatively  most 
marked  in  the  female,  abdominal  respiration  in  the  male. 

The  physiological  relations  of  costal  and  diaphragmatic 
respiration. 

The  "cardio — pneumatic  "  movements  of  respiration. 

In  forced  inspiration  the  chief  dilation  of  the  chest  is  caused 
in  both  sexes  by  elevation  of  the  ribs. 

The  movements  of  the  face,  pharynx  and  larynx  in  respir- 
ation. 

The  rhythm  of  respiration.  Time  relations  of  inspiration 
and  expiration. 

Effect  of  exercise,  position  of  body,  etc.,  on  the  rhythm. 

Methods  of  artificial  respiration. 

THE    QUANTITY   OF    AIR    IN  THE   LUNGS   AND   ITS 

VARIATION. 

After  the  most  violent  expiration  the  lungs  still  contain 
about  100  cubic  inches  of  air,  called  the  residual  air.  At  the 
end  of  an  ordinary  expiration  the  lungs  contain  an  additional 
100  cubic  inches  of  supplemental  air.  Thus  there  are  200  cubic 
inches  of  stationary  air  which  in  ordinary  breathing  never 
leave  the  chest.  In  ordinary  inspiration  and  additional  30  cubic 
inches  of  tidal  air  are  drawn  in.  By  a  forced  inspiration  there 
may  still  be  added  about  98  cubic  inches  of  complemental  air. 
The  full  capacity  of  the  lungs,  then,  is  328  cubic  inches;  the 
vital  capacity,  the  amount  of  air  capable  of  being  taken  in 
after  the  most  powerful  expiration,  is  228  cubic  inches.  These 
capacities  are  estimated  from  the  lungs  of  a  man  of  medium 
size.    The  relation  of  vital  capacity  to  stature. 

The  process  of  gas  interchange  in  the  lungs  under  these 
conditions. 


—60— 

The  quantity  of  air  breathed  daily. 

The  effect  of  respiration  upon  the  movement  of  blood  and 
lymph. 

THE  CHANGES  OF  AIR  IN  RESPIRATION. 

The  history  of  the  physiology  of  respiration. 

Chemistry  of  the  atmosphere.  Absolute  and  relative 
humidity. 

The  air  expired  is  nearly  always  warmer  than  that  inspired. 

About  five  per  cent,  of  the  heat  lost  to  the  body  goes  to 
warming  the  expired  air,  and  about  15  per  cent,  is  employed  in 
evaporating  the  water  of  respiration. 

The  air  expired  is  nearly  saturated  with  moisture. 

Oxygen.      Nitrogen.      Carbonic  Acid. 
Pure  dried  air  contains  in  100  vols.  20.81  79.15  .04 

Expired  air  contains  in  100  vols.  16.933        79.557  4.38 

The  expired  air  also  contains  small  but  important  quanti- 
ties of  volatile  organic  matters. 

The  volume  and  weight  of  oxygen  absorbed  and  carbonic 
acid  given  off  in  a  day. 

The  probable  chemical  connection  between  the  absorption 
of  O  and  the  excretion  of  C03  in  the  lungs. 

Owing  to  its  higher  temperature  and  contained  watery 
vapor  the  volume  of  air  expired  is  greater  than  that  inspired  ; 
but  when  dried  and  measured  at  the  same  temperature  the  air 
inspired  is  found  to  have  diminished  in  bulk,  having  lost  a 
greater  volume  of  oxygen  than  it  has  gained  of  carbonic  acid 
in  respiration. 

Ventilation.  The  hurtful  qualities  of  air  which  has  been 
respired  are  due  not  so  much  to  its  carbonic  acid  as  to  the  ani- 
mal matter  contained  in  it.  Insidious  influence  of  very  small 
quantities  of  matters  excreted  in  respiration.  The  increase  in 
pulmonary  diseases  under  conditions  of  ill-ventilation. 

For  purposes  of  health  each  person  in  a  room  should  be 
provided  with  a  volume  of  air  equal  to  800  cu.  ft.  and  this  should 
be  renewed  from  the  outside  at  the  rate  of  1  cu.  ft.  per  minute. 
For  sick  people  an  initial  space  of  at  least  1000  cu.  ft.  should 
be  furnished. 


—61— 

THE  CHANGES  UNDERGONE  BY  THE  BLOOD  IN  THE 

LUNGS. 

The  losses  and  gains  of  the  blood  in  the  lungs. 

The  difference  in  color  between  the  venous  and  arterial 
blood. 

When  exposed  to  a  vacuum  100  vols,  blood  give  off  about 
72  vols,  gas,  measured  at  0°O.  and  750  millimetres  pressure. 

Oxygen.      Carbonic  Acid.      Nitrogen. 

inn  ,r~i      Arterial  blood  „.  20  50  2 

100  vols.   Venoug   bloQd  give  1Q  6Q  2 

The  color  of  the  blood  of  an  asphyxiated  animal. 

The  color  of  the  blood  is  due  to  the  haemoglobin  contained 
in  the  red  corpuscles. 

Oxyhemoglobin  and  reduced-haemoglobin.  Haemoglobin 
crystals. 

Poisoning  by  carbon  monoxide  gas.  By  hydrogen  sulphide. 
Specific  action  of  various  deliterious  gases. 

The  spectroscopic  study  of  haemoglobin  and  its  derivatives. 

The  amount  of  gas  given  off  to  a  vacuum  by  blood  is 
greatly  in  excess  of  that  which  could  be  obtained  from  an  equal 
volume  of  blood  serum. 

The  laws  which  govern  the  absorption  of  gases  by  liquids. 

The  explanation  of  the  large  quantity  of  gas  found  in  blood 
is  the  chemical  union  of  the  oxygen  with  the  haemoglobin. 

The  combination  of  oxygen  with  haemoglobin  is  not  a  stable 
one,  but  the  gas  is  given  off  when  the  partial  pressure  of  oxy- 
gen upon  the  blood  falls  below  one  inch  of  mercury. 

Comparison  of  the  partial  pressures  of  gases  in  the  lung 
alveoli  and  in  the  blood. 

The  carbonic  acid  of  the  blood  exists  chiefly  in  loose  chem- 
ical combination  with  substances  in  the  plasma. 

The  respiration  of  the  tissues.  The  same  laws  determine 
the  gas  interchange  in  the  tissues  as  in  the  lungs. 

The  blood  in  the  left  side  of  the  heart  is  cooler  than  that 
im the  right  side  because  more  heat  is  lost  to  the  blood  in  the 
lungs  than  is  gained  by  the  oxidation  of  haemoglobin. 

The  ratio  of  the  amount  of  oxygen  absorbed  and  of  car- 
bonic acid  given  off  by  the  tissues  in  a  certain  time  is  not  con- 


—62— 

stant.  During  the  day  more  oxygen  is  given  off  in  carbonic 
acid  than  is  taken  up  in  the  same  time;  during  the  night  the 
proportions  are  reversed.  The  same  relation  holds  for  periods 
of  activity  and  of  rest. 

The  amount  of  oxygen  taken  into  the  blood  depends  not 
upon  the  amount  supplied  to  the  lungs  but  upon  the  amount 
which  has  been  used  by  the  tissues.  The  haemoglobin  of  arter- 
ial blood  is  normally  nearly  or  quite  saturated  with  oxygen. 
The  erroneous  idea  that  respiration  of  pure  oxygen  accelerates 
the  oxidations  of  the  body. 

The  oxidations  of  the  body  occur  not  in  the  blood  but  in 
the  tissues. 

THE   NERVOUS  MECHANISM  OF  THE   RESPIRATION. 

The  mixed  voluntary  and  involuntary  characters  of  the  re- 
spiratory movements. 

The  respiratory  centre  in  the  medulla  oblongata.  Instant 
cessation  of  respiratory  movement  follows  destruction  of  this 
centre. 

The  phrenic  nerves  spring  from  the  spinal  cord  at  about 
the  level  of  the  4th  pair  of  cervical  nerves ;  the  intercostal 
nerves  leave  the  cord  throughout  the  dorsal  region. 

The  modified  respiratory  movements  producing  speech,  etc* 

The  co-ordination  of  the  various  respiratory  movements. 

The  effect  upon  the  movement  of  cutting  a  nerve  supplying 
any  part  of  the  respiratory  apparatus. 

THE  CONDITIONS  UNDER  WHICH  THE  RESPIRATORY 
CENTRE  ACTS. 

The  movements  of  respiration  are  remarkably  susceptible 
to  modification  under  the  influence  of  stimuli  foreign  to  their 
nervous  centre ;  effect  of  a  dash  of  cold  water ;  effect  of 
emotions. 

When  any  single  efferent  respiratory  nerve  is  cut  the  part 
supplied  by  it  remains  quiescent ;  and  when  the  spinal  cord  is 
divided  below  the  medulla  the  failure  in  the  income  of  oxygen 
is  accompanied  by  an  exalted  action  of  the  respiratory  centre 
as  shown  by  the  more  powerful  action  of  the  remaining  respir- 


—63— 

atory  movements  of  the  mouth  parts,  though  these  are  ineffi- 
cient to  aerate  the  blood. 

When  the  vagi  are  divided  on  each  side  of  the  neck  the 
respiratory  movements  become  slower  and  deeper,  but  do  not 
cease. 

When  the  central  end  of  the  cut  vagus  is  gently  stimulated 
the  respiration  is  quickened,  and  it  may  be  so  hastened  that 
the  respirations  are  fused  together  and  the  muscles  come  to  a 
tetanic  standstill  in  the  phase  of  inspiration. 

When  the  central  end  of  a  superior  laryngeal  nerve  is 
stimulated  the  respiration  because  slower  and  deeper,  and  if 
the  stimulus  be  sufficiently  strong  expiratory  tetanus  is  pro- 
duced. 

The  same  is  true,  but  to  a  slighter  extent,  of  the  inferior 
laryngeal  nerve. 

It  is  not  improbable  that  the  mere  mechanical  conditions 
of  the  lung  in  the  phases  of  expiration  and  inspiration  excite 
the  respective  movements  of  inspiration  and  expiration. 

It  is  clear,  then,  that  the  respiratory  centre  is  under  the 
modifying  control  of  stimuli  proceeding  to  it  along  afferent 
nerves;  but  that  the  essential  activity  of  the  centre  is  quite  in- 
dependent of  any  stimulus  reaching  it  from  without. 

THE  EXCITING  CAUSE  OF   THE  RESPIRATORY 
MOVEMENT. 

The  action  of  the  respiratory  centre  is  determined  by  the 
condition  of  the  blood  supplying  it. 

The  centre  is  made  active  by  venous  blood,  but  is  not  ex- 
cited by  arterial  blood. 

It  appears  to  be  the  want  of  oxygen  and  not  the  excess  of 
carbonic  acid  which  stimulates  the  centre,  as  shown  by  the  re- 
spiratory disturbance  of  an  animal  breathing  in  an  atmosphere 
of  hydrogen. 

The  activity  of  the  respiratory  centre  is  determined  by  the 
direct  influence  of  the  blood  upon  it,  irrespective  of  the  condi- 
tion of  the  blood  in  other  parts  of  the  body. 

We  may  suppose  that  the  activity  of  the  respiratory  centre 
causes  an  accumulation  of  stimulating  waste  products  in  it, 


—64— 

and  that  the  oxygen  supplied  by  arterial  blood  combines  with 
and  renders  these  inert. 

The  change  of  normal  respiratory  rhythm  of  eupnwa  into 
that  of  dysp?ma. 

The  breathing  of  dyspnoea  owes  its  character  to  lack  of 
oxygen.  In  ordinary  dyspnoea  the  breathing  is  deeper  than 
usual  and  the  rhythm  generally  slower,  as  after  section  of  the 
phrenic  nerves.  In  the  dyspnoea  of  asthma,  however,  the  res- 
pirations are  quicker  and  rather  less  deep  than  usual. 

Dyspnoea  due  to  hemorrhage.    Heat  dyspnoea. 

Physiological  apncea  is  the  condition  of  rest  in  the  respira- 
tory centre  due  to  excessive  respiration.  Distinguish  from  pa- 
thological apncea. 

Apncea  of  the  foetus  in  utero,  and  the  cause  of  the  first  in 
spiratory  movement  at  birth.     Voluntary  production  of  apncea 
by  deep,  rapid  breathing. 

Modification  of  the  irritability  of  the  respiratory  centre. 
Low  irritability  in  the  foetus,  and  in  newly  born  animals.  The 
great  resistance  against  death  by  asphyxia  produced  in  an  ani- 
mal by  previous  long-continued  depression  of  blood-pressure 
maintained  by  stimulation  of  both  vagi. 

The  phenomena  of  respiration  and  circulation  witnessed  in 
an  animal  passing  from  the  stage  of  physiological  apnma  to  that 
of  asphyxia. 

THE  RHYTHMIC  ACTION  OF  THE  RESPIRATORY  CENTRE. 

The  respiratory  discharge  is  probably  the  resultant  of  two 
forces,  one  exciting  to  discharge  and  the  other  resisting  it. 
Many  mechanical  analogies  can  be  cited  showing  how,  under 
similar  conditions,  rhythmic  action  is  brought  about. 

The  waste  products  of  tissue  change  in  the  respiratory 
centre  are  probably  the  stimuli  to  its  discharge. 

The  function  of  the  afferent  respiratory  nerves  is  probably 
to  either  increase  or  diminish  the  exciting  as  compared  with 
the  resisting  force  in  the  centre. 

The  resistance  theory. 

The  double  nature  of  the  respiratory  centre :  the  inspira- 
tory centre;  the  expiratory  centre. 

The  phenomena  and  means  of  production  of  asphyxia. 

Poisoning  by  carbonic  oxide. 

Modified  respiratory  movements; — yawning;  sighing; 
coughing  ;  hiccough  ;  sneezing  ;  laughing  ;  sobbing. 


XI.   THE  SKIN  AND  ITS  APPENDAGES. 

The  skin  consists  of  two  layers,  an  outer  cellular  layer,  the 
epidermis  or  cuticle,  and  an  inner  layer  composed  chiefly  of 
connective  tissue,  the  dermis,  cutis  vera  or  corium. 

The  hairs  and  nails  are  local  modifications  of  the  epi- 
dermis. 

HISTOLOGICAL   STRUCTURE  OF  THE   SKIN  AND   ITS 
APPENDAGES. 

The  dermis  : — its  structural  tissue;  the  papillas — their  ar- 
rangement in  rows;  its  blood  vessels,  nerves,  tactile  corpuscles 
and  Pacinian  bodies ;  groups  of  fat  cells. 

The  epidermis :  soft  and  horny  epidermis ;  the  lower  layer 
of  perpendicular  cells;  the  pigmented  cells  of  dark  races; 
nerve  endings  ;  cause  of  external  ridges. 

The  nails. 

The  sudoriparous  or  sweat  glands ;  the  spiral  opening  and 
the  coiled  inner  termination. 

Hair;  the  papilla  and  hair  follicle;  the  hair  muscles;  the 
erectile  tissue  about  the  base  of  sensory  hairs. 

The  sebaceous  or  oil  glands. 

THE  SECRETION  OF  THE  SWEAT  GLANDS. 

The  functions  of  the  perspiration  are  to  remove  waste  mat- 
ters trom  the  body,  and  to  serve  as  a  regulator  of  the  body  tem- 
perature. 

The  conditions  determining  the  amount  of  perspiration : — 
temperature;  moisture  of  the  air;    exercise;    nature  of  food. 

The  quantity  of  sweat  secreted  in  twenty-four  hours,  four 
to  forty  pounds. 

Sensible  and  insensible  perspiration. 

The  sweat  is  alkaline  in  reaction  and  owes  its  odor  to 
volatile  oils. 

Composition  of  the  perspiration ; — water ;  fatty  acids  ; 
sodium  chloride ;  urea. 


—66— 

THE  MECHANISM  OF  THE  SWEAT  SECRETION. 

An  increased  now  of  blood  to  the  skin  usually  attends  the 
production  of  perspiration,  but  is  not  the  cause  of  it.  The  dry 
skin  of  fevered  patients. 

The  emotion  of  terror  may  cause  sweating  from  a  pale 
skin. 

Sweat  is  produced  by  the  activity  of  the  cells  of  the  sudor- 
iparous glands  under  control  of  the  nervous  system. 

Sweat  centres  in  the  spinal  cord. 

Venosity  of  the  blood  stimulates  the  sweat  centres.  Sweat 
of  the  death  agony. 

Section  of  the  sciatic  nerve  of  the  cat  causes  reddening  of 
the  balls  of  the  feet,  but  no  sweating.  Stimulation  of  the  per- 
ipheral end  of  the  nerve  causes  the  secretion  to  appear  upon 
balls  of  the  feet  even  of  a  freshly  amputated  leg. 

Sweating  as  a  reflex  action. 

Pilocarpin  excites  to  activity  the  sweat  glands  and  perhaps 
the  centres  also ;  atropin  abolishes  their  functions ;  nicotin 
stimulates  the  sweat  centre. 

Importance  of  skin  as  an  excretory  organ ;  fatal  effect  of 
covering  an  animal  with  impervious  clothing.  Seguin  estimates 
that  seven  grains  of  matter  are  given  off  by  the  lungs  and 
eleven  grains  by  the  skin  in  a  minute. 

Respiration  by  the  skin  is  apparently  unimportant ; 
through  that  channel  a  man  throws  off  4-10  grms.  of  C02  in  a 
day  and  absorbs  about  the  same  amount  of  oxygen.  The  daily 
gas  exchange  by  the  lungs  is  about  800  grms.  C02  and  700 
grms.  oxygen. 

Absorption  by  the  skin  does  not  perceptibly  occur,  except 
of  substances  in  a  fatty  vehicle. 

The  secretion  of  the  sebaceous  glands. 


XII.   THE  KIDNEYS  AND  THEIR  SECRETION, 

GROSS  STRUCTURE  OF  THE  KIDNEY. 

The  capsule  surrounding  and  vessels  entering  the  kidney. 

The  hilum  ;  pelvis;  calices.  The  cortical  and  medullary 
portions  of  the  opened  kidney  ;  the  papilla?.  The  pyramids  of 
Malpighi  and  of  Ferrein. 

MICROSCOPIC  STRUCTURE  OF  THE  KIDNEY. 

The  uriniferous  tubules;  the  Malpighian  corpuscles;  the 
loops  of  Henle ;  the  convoluted  and  collecting  parts  of  the 
tubules.     The  ciliated  cells  of  the  convoluted  parts. 

The  lining  cells  peculiar  to  the  different  parts  of  the 
tubules. 

The  blood  supply  of  the  kidney  ;  the  glomeruli. 

THE  URINE. 

The  quantity  secreted  in  24  hours  varies  from  40  to  60  fluid 
ounces. 

The  complementary  activity  of  skin  and  kidneys. 
The  color,  reaction  and  specific  gravity  of  urine. 
The  variation  of  color  and  specific  gravity. 

THE  AMOUNT  AND  COMPOSITION  OF  URINE  PASSED  BY  A 
MEDIUM  SIZED  MAN  IN  TWENTY-FOUR  HOURS.  (Foster's 
Physiology.) 

Water 1,500  000  grammes 

Total  solids 72.000  grammes 

Urea 33.180  grammes  Chlorine 7.000  grammes 

Uric  acid .555  grammes  Ammonia .770  grammes 

Hippuric  acid__  .400  grammes  Potassium 2.500  grammes 

Pigment,  fats, etc  10.000  grammes  Sodium 11.090  grammes 

Sulphuric  acid-  2.012  grammes  Calcium .2G0  grammes 

Phosphoric  acid  3. 164  grammes  Magnesium .207  grammes 

The  ash  of  urine  is  nearly  the  same  as  the  inorganic  matter 
directly  determined,  which  indicates  that  the  substances  of  the 
9 


urine  contain  little  potential  energy.     It  is  different  with  re- 
gard to  the  ash  of  blood. 

The  general  nature  and  origin  of  the  various  substances 
found  in  the  urine. 

THE  SECRETORY  MECHANISM. 

The  uriniferous  tubule  consists  of  two  parts,  each  of  which 
probably  serves  special  purposes.  The  thin-walled  capsules 
round  the  glomeruli  probably  allow  rapid  filtration  of  water 
and  salts  through  them,  while  the  cells  lining  the  tubules 
proper  have,  no  doubt,  the  function  of  active  secretion. 

The  branches  of  the  renal  artery  have  nearly  a  straight 
course  to  the  glomeruli,  and  it  is  the  efferent  vessels  from  these 
which  form  the  capillaries  of  the  tubules. 

INFLUENCES   DETERMINING   THE  AMOUNT  OF   THE   SE- 
CRETION. 

Increased  flow  of  blood  to  the  kidney,  bringing  about  a 
high  blood -pressure  in  the  glomeruli,  increases  the  amount  of 
urine  secreted.  This  may  follow  general  rise  of  blood  pressure 
or  local  dilatation  of  the  renal  arteries.  The  anatomical  rela- 
tions of  the  capillaries  of  the  glomeruli  and  those  of  the 
tubules  indicate  that  changes  in  arterial  blood-pressure  operate 
chiefly  upon  the  former. 

The  effect  of  cold  in  constricting  the  vessels  of  the  skin  is 
to  raise  general  blood-pressure. 

Complementary  action  of  skin  and  kidneys. 

Dilution  of  the  blood  increases  the  secretion. 

Anything  which  lowers  the  vitality  of  the  cells  of  the 
glomeruli  diminishes  their  power  of  restraining  the  filtration  of 
substances,  as  albumin,  usually  retained  by  them.  Temporary 
albuminuria  produced  by  brief  occlusion  of  the  renal  artery. 

Stoppage  of  the  secretion  after  section  of  the  spinal  cord. 

THE  SECRETORY  EPITHELIUM  OF  THE  TUBULES. 

It  is  probable  that  the  cells  lining  the  tubules  have  the 
power  of  active  secretion  independent  of  blood  flow. 

The  passage  of  indigo-carmine  through  the  renal  cells. 
The  injection  of  urea  or  urates  excites  the  flow  of  urine. 


—69— 

The  process  of  secretion  as  studied  in  the  kidney  of  an 
amphibian. 

The  distinction  between  selection  by  the  kidney  cells  of 
urea  from  the  blood  and  the  manufacture  of  it  by  them  from 
certain  antecedents. 

The  evidences  as  to  the  part  played  by  the  kidney  cells  in 
the  elimination  of  urea. 

The  physiology  of  micturition. 


XIII.   THE  PHYSIOLOGY  OF  SECRETION. 

All  the  phenomena  of  secretion  probably  depend  in  the 
end  for  their  occurrence  on  the  physical  laws  of  diffusion  and 
filtration. 

The  nature  of  the  laws  regulating  the  diffusion  and  filtra- 
tion of  fluids  and  gases. 

Simple  application  of  the  laws  of  diffusion  in  tire  living 
body.  The  production  of  diarrhoea  by  the  presence  of  magne- 
sium salts  in  the  intestine.  The  interchange  of  matter  between 
the  lymph  and  the  blood  and  the  relation  of  the  animal  cell  to 
the  process.     The  gas  exchange  in  the  lungs. 

Secretion  is  not  simply  a  process  of  diffusion  and  filtration 
through  dead  membranes.  The  diffusion  membrane  of  secre- 
tion is  alive. 

In  the  simplest  form  of  true  secretion  certain  substances 
are  selected  by  and  passed  through  the  secreting  membrane. 
But  most  secreted  fluids  contain  specific  matters  which  have 
been  produced  by  the  vital  activity  of  secretory  cells. 

The  typical  secretory  animal  membrane :  (1)  the  secretory 
cell;  (2)  the  basement  membrane;  (3)   the  capillary  network. 

The  modification  of  the  typical  secretory  membrane  into 
glands. 

Various  forms  of  glands :  tubular  and  racemose  glands. 

The  parts  of  a  gland  :  the  duct ;  the  acinus  or  alveolus. 

The  circulation  in  glandular  tissue. 

Enzym.    Mucous  and  albuminous  glands. 

THE  PHENOMENA  OF   SECRETION  AS  DETERMINED 
IN  THE  SUB-MAXILLARY  GLAND. 

The  nerve  supply  of  the  gland,  and  the  processes  of  normal 
secretion. 

THE  CHEMICAL  CONSTITUTION  OF  SALIVA. 

The  proportions  of  water,  salts  and  organic  matters.    The 


-72— 

relative  diffusibility  of  the  constituents.    The  specific  bodies 
of  the  secretion. 

THE  CHANGES  PRODUCED  IN  THE  SUB-MAXILLARY 
GLAND  BY  STIMULATING  THE  PERIPHERAL  END  OF 
THE  CHORDA  TYMPANI  NERVE. 

The  dilation  of  the  blood  vessels ;  the  venous  pulse  and 
red  blood  in  the  veins.     Vaso-dilator  nerves. 

The  volume  of  fluid  continuously  secreted  may  exceed  that 
of  the  gland ;  the  fluid  could  therefore  not  have  been  all  stored 
in  the  resting  gland,  but  must  have  come  from  the  blood  dur- 
ing the  stimulation. 

The  saliva  is  not  simply  filtered  from  the  blood,  for  the 
secretion  still  goes  on  when  the  pressure  of  saliva  within  the 
duct  exceeds  that  of  the  blood  in  the  artery  of  the  gland. 

Fibres  of  the  chorda  tympani  must  control  the  secretory 
activity  of  the  gland  cells ;  for,  after  poisoning  with  atropin, 
stimulation  of  the  chorda  still  produces  vaso-motor  dilatation 
in  the  gland,  but  causes  no  secretion. 

The  antagonistic  actions  of  atropin  and  pilocarpin. 

The  watery  fluid  of  the  secretion  must  have  been  contained 
in,  and  actively  forced  out  of,  the  gland  cells. 

The  secretion  obtained  by  artificial  stimulation  from  the 
gland  of  a  decapitated  animal. 

The  chief  volume  of  the  secretion  consists  of  the  easily 
filtered  and  diffusible  water  with  salts  in  solution. 

The  volume  of  fluid  secreted  in  a  given  time  does  not 
markedly  diminish  during  a  series  of  stimulations. 

The  organic  matters  of  the  saliva  are  not  readily  dffusible. 

The  organic  matters  decrease  in  quantity  as  secretion  pro- 
gresses. They  are  probably  made  by  and  stored  up  within  the 
gland  cells. 

The  temperature  of  saliva  in  the  gland  duct  is  higher  than 
that  of  the  blood. 

NERVES  WHICH  REGULATE  THE  CHEMICAL  NATURE  OF 
THE  GLAND  CELL  SUBSTANCE. 

When  the  sympathetic  nerve  supplying  the  sub-maxillary 
gland  of  the  dog  is  stimulated,  the  blood  vessels  of  the  gland 


—73— 

contract  and  the  amount  of  secretion  is  insignificant  and  is 
viscid  in  consistency.  The  chorda  saliva  is  more  abundant 
and  less  viscid  than  the  sympathetic. 

Stimulation  of  the  peripheral  end  of  the  nerve  of  Jacobson 
in  the  dog  produces  an  abundant  secretion  from  the  parotid 
gland. 

Stimulation  of  the  peripheral  end  of  the  sympathetic  sup- 
plying the  parotid  gland  of  the  dog  causes  no  secretion,  but 
greatly  increases  the  organic  content  of  the  secretion  produced 
by  subsequent  stimulation  of  the  nerve  of  Jacobson. 

Nerves  of  three  distinct  physiological  varieties  can  be 
shown  to  take  part  in  secretion  :  (1)  Vaso-motor  nerves,  which 
regulate  the  calibre  of  the  blood  vessels ;  (2)  secretory  nerves, 
which  bring  about  the  active  diffusion  of  water  and  salts 
through  the  gland  cells ;  (3)  trophic  nerves,  which  produce 
chemical  changes  in  the  gland  substance,  giving  rise  to  more 
soluble  organic  matters  in  it. 

THE  HISTOLOGICAL  CHANGES  OF  THE  SALIVARY 
GLANDS  IN  SECRETION. 

Comparison  of  the  appearance  and  reaction  toward  stain- 
ing reagents  of  a  resting  sub-maxillary  gland  with  one  which 
has  abundantly  secreted. 

Comparison  of  the  histological  characters  of  the  parotid 
gland  before  and  after  stimulation  of  the  sympathetic  nerve. 

Disappearance  of  the  granules  from  the  outer  parts  of  the 
cells  during  secretion. 

The  paralytic  secretion  of  saliva. 

The  theory  of  secretion  suggested  by  the  facts  that  have 
been  advanced. 


XIV.   THE  VARIETIES  AND  FUNCTIONS  OF  INGESTA. 

The  body  must  depend  upon  food  matters  for  the  mainten- 
ance of  its  structure  and  as  the  source  of  its  energy.  The 
nature  of  the  alimentary  substances  which  might  be  supposed 
most  readily  to  fulfill  these  functions. 

The  loss  of  energy  to  the  food  in  the  body. 

The  source  of  energy  of  plant  life. 

The  different  kinds  and  chemical  composition  of  the  sub- 
stances entering  into  food  stuffs  :  proteids ;  albuminoids;  fats  ; 
carbohydrates;  salts  and  water;  condiments,  etc. 

The  physical  and  chemical  characters,  and  chemical  reac- 
tions of  the  various  kinds  of  alimentary  substances. 

Proteids  form  the  only  class  of  foods  which  can  probably 
alone  maintain  life  ;  but  the  normal  diet  contains  all  the  differ- 
ent kinds  of  food  matter. 

The  history  of  the  various  food  stuffs  in  the  body,  and  the 
form  under  which  they  appear  in  the  egesta. 

In  general,  the  nitrogen  of  foods  reappears  in  the  crystalline 
bodies  of  the  excreta,  and  hydrocarbons  and  carbohydrates  re- 
appear as  water  and  carbonic  acid. 

Liebig's  classification  of  foods  into  plastic  and  respiratory. 
Objections  to  this  division. 

CLASSIFICATION  OF  INGESTA. 

f  Supply  material  for  the  forma- 

!  tion  and  restoration  of  tissues. 

Foods   •{  Supply  the   energy  for  the 

|  construction  and  activity  of 

[  the  body. 


Ingesta : 


Do  not  as  such  form  a  part  of 
the  living  tissues,  but  are  me- 
dia necessary  to  their  activity. 
A  second  class  of  them  acts 

Force  regulators  i  as  a  collection  of  stimulating 
substances  which  produce 
effects  out  of  proportion  to 
the  amount  of  material  em- 
ployed. 

10 


-76— 

Any  ingested  substance  is  not  restricted  in  its  function  to 
one  of  the  above  classes,  but  may  probably  at  the  same  time 
supply  energy  and  tissue  material  to  the  body,  and  serve  as  a 
force  regulator  to  the  activities  of  the  body. 

The  two  kinds  of  force  regulators  represented  by  a  saline 
solution  and  a  condiment. 

Force  regulators  may  produce  their  eifects  reflexly  by  act- 
ing on  a  peripheral  organ,  or  directly  by  coming  in  contact  with 
the  internal  protoplasm  The  profound  importance  of  such 
stimuli. 

The  force  regulating  power  of  drugs. 

The  usefulness  of  cooking. 


XV,   DIGESTION;  AND  THE  ACTIVITIES  AND  STRUCTURE  OF 
THE  PARTS  INVOLVED  IN  IT. 

THE  STRUCTURE  AND  ARRANGEMENT  OF  THE 
MOUTH  PARTS. 

The  anatomy  of  the  buccal  cavity  and  parts  in  connection 
with  it.  The  sub-maxillary,  the  parotid  and  the  sub-lingual 
glands  and  their  openings. 

Structure  of  the  buccal  mucous  membrane. 

The  tongue  ;  its  muscles,  nerves  and  papillae. 

The  muscles  of  the  pharynx  and  the  valve  like  action  of 
the  soft  palate. 

The  teeth  ;  the  two  sets  of  permanent  and  milk  teeth  ;  the 
number  in  each.  The  shape  and  parts  of  the  various  teeth. 
The  crusta  petrosa  ;  dentine;  enamel. 

THE  PHYSIOLOGY  OF  SALIVA. 

Saliva  as  found  in  the  mouth  is  the  mixed  product  of  the 
three  pairs  of  salivary  glands,  of  the  glands  of  the  tongue  and 
adjacent  parts,  and  of  the  buccal  epithelium. 

The  physical  and  chemical  characters  of  saliva. 

The  solid  bodies  found  in  saliva ;  the  food  detritus  ;  epithel- 
ium cells  ;  "  salivary  corpuscles." 

The  function  of  saliva  in  assisting  deglutition. 

The  physiological  process  of  secretion  and  influences  mod- 
ifying it.  "  Watering  "  of  the  mouth  ;  the  "  rice  ordeal."  The 
normal  reflex. 

Quantity  of  saliva  secreted. 

THE  DIASTATIC  ACTION  OF  SALIVA. 

The  conversion  of  starch  into  sugar  under  the  action  of 
saliva.    The   greater  part  of   the   sugar  which   is  formed  is 

maltose. 


—78- 

The  influence  of  temperature  on  the  rapidity  of  the  diasta- 
tie  action. 

Exposure  to  the  temperature  of  boiling  water  destroys  the 
diastatic  power  of  saliva.  The  action  is  arrested  in  a  medium 
containing  as  much  as  0.  1  HC1  free,  and  strong  alkalis  destroy 
the  body  in  the  saliva  which  produces  the  change. 

The  amount  of  starch  which  may  be  changed  into  sugar 
bears  no  definite  relation  to  the  amount  of  saliva  employed. 
The  diastatic  power  of  the  saliva  does  not  seem  to  decrease 
proportionately  to  the  extent  of  the  change  which  it  brings 
about. 

The  diastatic  action  of  saliva  is  due  to  the  presence  in  it  of 
an  animal  ferment,  Ptyalin,  which  is  probably  an  organic  but 
non-proteid  product  of  the  activity  of  the  salivary  glands. 

The  diastatic  action  of  saliva  is  more  vigorous  in  a  neutral 
than  in  an  alkaline  solution.  The  effect  of  peptones  on  the 
activity  of  ptyalin. 

The  distinctive  characters  of  ferments.  Organized  and 
unorganized  ferments. 

The  special  characters  of  the  saliva  obtained  from  different 
glands. 

THE  PKOCESS  OF  DEGLUTITION. 

The  masticated  mouthful  of  food  is  brought  together  in  a 
heap  upon  the  back  of  the  tongue,  and  thence,  by  a  compli- 
cated series  of  co-ordinated  movements,  is  transferred  to  the 
stomach. 

The  protective  movements  of  the  respiratory  apparatus, 
and  the  function  of  the  epiglottis. 

The  co-ordination  of  movement  in  the  mouth  parts  in  pho- 
nation,  deglutition,  etc. 

The  process  of  deglutition  may  be  divided  into  three  stages: 
(1)  while  the  food  is  still  within  the  mouth,  the  movement  is 
purely  voluntary  and  may  be  slow  or  rapid.  (2)  When  the 
food  reaches  the  common  buccal  and  respiratory  chamber  of 
the  pharynx,  the  movement  is  nearly  purely  reflex,  or  involun- 
tary, and  is  then  more  rapid.  (3)  When  the  food  reaches  the 
oesophagus  its  movement  is  again  slower  and  quite  involuntary, 


—79- 

and  the  mouthful  is  carried  by  a  peristaltic  contraction  to  the 
stomach. 

The  nervous  mechanisms  involved  in  the  swallowing  move- 
ment.    The  centre  in  the  medulla. 

The  histological  structure  of  the  oesophagus. 

The  mechanisms  and  processes  involved  in  vomiting. 
The  stimulus  to  the  movement  may  be  either  peripheral  or 
central.     Majendie's  experiment.     Nausea. 

THE  STRUCTURE  AND  PHYSIOLOGY  OF  THE 
STOMACH. 

THE  ANATOMY  AND  HISTOLOGY  OF  THE  STOMACH. 

The  shape,  anatomical  connections,  and  nervous  and  vascu- 
lar supply  of  the  stomach.     The  fundus. 

The  empty  stomach  is  always  contracted. 

The  three  coats  of  the  stomach  :  (1)  muscular;  (2)  areolar; 
(3)  mucous. 

The  muscular  coat  is  composed  of  unstriated  tissue.  Its 
layers  of  longitudinal,  oblique  and  circular  fibres. 

The  cardiac  and  pyloric  sphincters.     The  pyloric  "  valve." 

The  areolar  coat.     Division  of  blood-vessels  in  it. 

The  mucous  membrane.    The  rugae  and  their  cause. 

The  shape  and  cellular  elements  of  the  glands  of  the  mu- 
cous membrane.  The  difference  between  the  glands  of  the 
pyloric  and  other  regions  of  the  stomach.  The  blood  and 
lymph  vessels  of  the  mucous  membrane. 

The  nerve  cells  within  the  stomach  wall. 

THE  GASTRIC  JUICE  AND  ITS  SECRETION. 

The  fluid  obtained  from  the  stomach  of  a  dog  with  gastric 
fistula  by  means  of  electrical,  mechanical,  or  chemical  stimula- 
tion of  the  mucous  membrane.  Dilute  alkalis  readily  excite 
the  secretion. 

Flushing  of  the  mucous  membrane  during  digestion. 

The  quantity  of  gastric  juice  secreted  in  24  hours. 


—80— 

THE  CHEMISTY  OF  THE  GASTRIC  JUICE. 

The  gastric  juice  of  the  dog  contains  about  0.45  p.  c.  solid 
matter,  of  which  half  is  inorganic  saline,  and  half  organic  mat- 
ter, the  ferment  pepsin,  mucus,  etc.  The  reaction  is  always 
acid,  due  to  the  presence  of  free  HOI.  Lactic  and  butyric  acids, 
which  are  frequently  present,  are  probably  due  to  fermenta- 
tions of  the  food  matter,  and  not  to  the  secretoiy  activity  of 
the  stomach.  The  amount  of  free  HC1  is  about  0.2  p.  c.  of  that 
of  the  normal  juice. 

The  secretion  of  gastric  juice  is  not  continuous,  but  de- 
pends upon  stimulation  of  the  mucous  membrane.  The  relation 
of  absorption  from  the  stomach  to  the  amount  and  quality  of 
the  juice  secreted. 

The  variation  in  the  quantity  and  quality  of  the  gastric 
juice  at  different  stages  of  secretion. 

THE  DIGESTIVE  POWERS  OF  THE  GASTRIC  JUICE. 

The  proteolytic  digestive  powers  of  the  gastric  juice  are 
due  to  the  action  of  a  ferment  pepsin,  which  is  made  in  and  se- 
creted by  the  cells  of  the  stomach  glands.  Pepsin  is  probably 
an  organic  but  non-proteid  body. 

The  presence  of  free  acid  is  necessary  to  the  action  of  gas- 
tric juice.  The  power  of  the  juice  is  destroyed  by  the  temper- 
ature of  boiling  water.  The  rapidity  of  digestion  depends 
upon  the  temperature. 

On  starch  the  gastric  juice  has  no  effect,  though  it  may  set 
free  starch  grains  which  are  held  together  by  proteid  substances. 

The  glands  of  the  stomach  appear  to  secrete  a  ferment 
which  changes  grape  sugar  to  maltose,  and  the  mucus  of  the 
superiicial  epithelium  contains  a  ferment  capable  of  changing 
cane  sugar  to  maltose.  An  excess  of  cane  sugar  in  food  causes 
an  increased  secretion  of  mucus. 

The  mechanical  function  of  the  mucus  as  a  cleanser  of  the 
alimentary  canal. 

On  fats  the  gastric  juice  has  no  effect,  though  they  are  set 
free  by  the  solution  of  the  proteid  and  gelatiniferous  portion  of 
their  cell  envelopes. 

Albuminoid  substances  are  dissolved  by  the  gastric  juice. 


—81— 

Such  mineral  salts  as  are  soluble  in  dilute  acids  are  dis- 
solved by  gastric  juice. 

The  chief  digestive  power  of  the  gastric  juice  consists  in 
its  decomposition  of  proteids  by  which  they  are  converted  into 
soluble,  diffusible  substances  called  peptones. 

Experiments  upon  the  digestive  power  of  gastric  juice  may 
be  carried  out  either  with  natural  or  artificial  juice. 

Artificial  gastric  juice  may  be  prepared  by  extracting  the 
minced  mucous  membrane  of  the  stomach,  (1)  with  water,  (2) 
with  dilute  hydrochloric  acid  (0.2  p.  c),  (3)  with  glycerin,  (1) 
or  with  glycerin  after  standing  under  strong  alcohol. 

Gastric  juice  acts  most  rapidly  at  about  the  body  tempera- 
ture, and  is  inert  at  0°C. 

The  presence  of  free  acid,  best  HC1  0.2  p.  c,  is  necessary  to 
the  activity  of  the  juice. 

The  acid  is  used  up  in  digestion  and  gradually  disappears 
from  an  artificial  solution. 

The  ferment,  pepsin,  does  not  appear  to  be  used  up  in 
digestion. 

Evidence  that  pepsin  is  formed  by  changes  in  the  stomach 
glands  after  death ;  that  it  is  made  during  secretion  and  not 
stored  up  in  the  cells. 

The  pro-ferment,  pepsinogen. 

The  activity  of  the  gastric  j  uice  is  greatly  hindered  by  the 
accumulation  of  the  products  of  digestion. 

The  histological  changes  which  the  gastric  gland  cells  un- 
dergo in  digestion. 

The  changes  as  to  granulation  which  digestive  cells  in  gen- 
eral go  through  in  their  activity. 

The  functions  of  the  different  kinds  of  cells  of  the  stomach 
glands.  The  relation  of  the  glands  in  the  pyloric  part  of  the 
stomach  to  those  in  other  regions  of  the  organ. 

The  milk  ferment.    Rennet. 

The  gastric  juice  has  antiseptic  properties. 

THE  CHANGES  OF  PROTEIDS  IN  GASTRIC  DIGESTION. 

The  characteristic  swelling  of  the  proteid  substance  and  its 
gradual  solution. 

The  formation  of  soluble  albumin,  precipitable  by  boiling. 


—82— 

The  formation  of  parapeptone  or  acid  albumin.  Dilute 
acid  alone  may  effect  these  changes. 

The  formation  of  peptone.     Dyspeptone. 

Meissner's  A,  B,  and  0  peptones. 

Complete  and  incomplete  peptones. 

Characters  of  perfect  peptones:  peptones  are  soluble  in 
water,  but  are  not  precipitated  by  boiling;  they  answer  the 
chemical  tests  for  proteicls ;  they,  unlike  other  proteids,  are 
readily  diffusible.  They  are  not  precipitated  by  strong  acetic 
acid  and  potassium  ferrocyanide,  as  are  the  incomplete  pep- 
tones. 

Kuhne's  theory  of  the  division  of  proteid  substances  by 
gastric  digestion  into  two  groups — Hemi- peptone  and  Anti- 
peptone. 

The  formation  of  peptones  appears  to  be  brought  about  by 
a  hydration  of  the  proteid. 


THE  HISTORY  OF  THE   FOOD   WITHIN   THE  MOUTH 
AND  STOMACH. 

The  effect  of  mastication,  and  the  mechanical  and  chemical 
functions  of  saliva. 

The  swallowed  saliva  excites  the  flow  of  gastric  juice,  as 
does  probably  the  mere  smell  of  food. 

The  digestive  action  of  saliva  upon  starch  is  not  interfered 
with  by  the  acidity  of  the  gastric  juice  to  the  same  extent  as 
would  be  the  case  in  a  pure  acid  of  the  same  strength. 

The  mechanical  and  chemical  changes  of  the  food  in  the 
stomach.  The  usefulness  of  thorough  mastication.  The  me- 
chanical dissolution  of  the  fats,  starches,  and  proteids.  The 
nature  of  the  movement  of  food  in  the  stomach.  The  chyme. 
The  processes  of  solution,  absorption,  and  passage  into  the  in- 
testine. 

The  rapidity  of  digestion  in  the  stomach  and  influences 
modifying  it;  nature  of  the  food;  method  of  cooking;  state  of 
division;  temperature;  rate  of  absorption  ;  the  efficiency  of  the 
gastric  juice  and  rapidity  of  its  secretion;  the  energy  of  move- 
ment which  mixes  the  food. 


—83— 

THE  MECHANISMS  OF  SECRETION   AND   OF  MOVE- 
MENT IN  THE  STOMACH. 

The  only  nerves  reaching  the  stomach  are  branches  from 
the  vagi  and  the  splanchnics. 

Normal  gastric  juice  is  secreted  after  division- of  both  sets 
of  nerves.  The  essential  secretory  mechanism  seems  to  be 
local.  The  food  is  brought  directly  into  contact  with  the  secre- 
tory membrane. 

The  influence  of  emotions  on  secretion. 

The  normal  mucous  membrane  is  flushed  daring  digestion ; 
it  becomes  pale  on  cutting  through  the  vagi,  and  reddens  again 
when  the  central  ends  of  these  nerves  are  stimulated. 

Afferent  vaso-motor  impulses  seem  to  travel  from  the 
stomach  along  the  vagi,  while  efferent  vasomotor  impulses  de- 
scend to  the  stomach  in  the  splanchnic  fibres. 

The  nature  and  cause  of  the  movements  of  the  stomach. 
•  The  empty  stomach  is  contracted ;  the  empty  intestine  is 
relaxed. 

The  influence  of  mechanical  distention  on  the  movement 
of  the  stomach. 

The  influence  of  extrinsic  nerves  upon  movement  and  se- 
cretion. 

Vomiting. 


THE  CHANGES  WHICH  THE  FOOD  UNDERGOES  IN 
THE  INTESTINE,  AND  THE  DIGESTIVE  ORGANS 
INVOLVED  IN  THEM. 

The  digestive  fluids  which  are  poured  into  the  intestine  are 
all  alkaline  in  reaction  and  come  from  three  sources:  (1)  the 
Pancreas,  pancreatic  juice;  (2)  the  Intestinal  Mucous  Mem- 
brane succus  entericus;  the  Liver,  hile. 

THE  ANATOMY  AND  HISTOLOGY  OF  THE  PANCREAS. 

The  relative  position  of  the  openings  of  the  bile  and  pan- 
creatic ducts  into  the  intestine  in  man  and  in  other  animals. 
The  lobulated  structure  of  the  gland. 

The  histological  appearance  of  the  pancreas.    The  ducts  ; 
ii 


—84— 

the  single  acini;  the  gland  cells,  their  outer  hyaline  and  inner 
granular  zone. 

The  phases  of  histological  change  which  the  gland  cells 
undergo  in  digestion.  The  observation  of  the  pancreas  in  a 
living  rabbit. 

In  general,  the  granular  matter  of  a  resting  secretory  cell 
is  distributed  throughout  the  whole  of  the  cell ;  while  as  a 
result  of  activity  the  granules  are  fewer  in  number  and  are 
accumulated  round  the  lumen  of  the  gland  on  the  inner  border 
of  the  cells. 

The  difficulty  of  establishing  a  permanent  pancreatic  fistula. 

The  pancreatic  juice  begins  to  flow  from  a  fistula  immedi- 
ately on  food  being  taken ;  the  rate  of  secretion  increases  till 
about  the  fourth  hour,  then  decreases  for  an  hour,  and  then 
increases  again,  reaching  a  second  maximum  at  the  eighth  hour 
after  taking  food,  afterwards  declining. 

The  amount  of  pancreatic  juice  secreted  in  24  hours. 

THE  CHARACTERS  AND  POWERS  OF  PANCREATIC  JUICE. 

Normal  pancreatic  juice  is  a  clear,  viscid  fluid,  frothing 
when  shaken,    It  has  a  decided  alkaline  reaction. 

The  fluid  contains  about  8  p.  c.  solids,  consisting  of  albumin, 
alkali  albumin,  leucin  and  tyrosin,  some  fats  and  soaps,  and  a 
considerable  amount  of  soda  carbonate.  The  presence  of  leucin, 
tyrosin  and  soaps,  is  probably  due  to  digestive  changes  in  the 
juice  after  its  secretion. 

The  pancreatic  juice  is  probably  the  most  important  of  all 
the  digestive  fluids.  It  probably  normally  contains  several  dis- 
tinct kinds  of  ferment. 

The  action  of  the  pancreatic  juice  upon  starch  is  similar  to 
that  of  saliva,  but  is  apparently  more  powerful. 

Neutral  fats  are  emulsified  by  pancreatic  juice,  and  are 
partly  decomposed  into  glycerine  and  a  fatty  acid. 

Unlike  the  gastric  juice,  pancreatic  juice  does  not  dissolve 
gelatiniferous  substances. 

On  proteids,  pancreatic  juice  exercises  a  powerful  solvent 
action,  converting  them  into  peptones. 

The  digestion  of  proteids  does  not  cease  at  this  stage,  but 


—85— 

peptones  are  further  decomposed  into  two  nitrogenous  crystal- 
line bodies,  leucin  and  tyrosin. 

The  complicated  changes  undergone  by  proteids  in  their 
digestion;  the  by-products  formed  are  alkali- albuminates  in- 
stead of  acid-albuminates  as  in  the  case  of  gastric  digestion. 

The  special  proteid  ferment  of  the  pancreatic  juice  is  called 
trypsin. 

Kiihne's  theory  of  the  changes  undergone  by  proteids  in 
gastric  and  pancreatic  digestions. 

The  digestion  of  proteids  by  natural  or  artificial  pancreatic 
juice  in  an  alkaline  medium  is  attended  with  the  formation  of 
indol,  a  substance  having  an  offensive,  feecal  odor. 

Indol  is  not  formed  when  the  digestion  is  carried  on  in  the 
presence  of  salicylic  acid.  It  is  probably  not  a  product  of 
digestion,  but  of  the  activity  of  adventitious  organized  fer- 
ments. 

A  proteid,  as  fibrin,  undergoing  pancreatic  digestion,  ap- 
pears to  be  gradually  corroded  and  crumbled;  it  does  not  swell 
as  when  acted  on  by  the  gastric  juice. 

If  the  pancreatic  ferments  be  exposed  to  the  temperature 
of  boiling  water  their  digestive  power  is  destroyed. 

An  artificial  extract  of  the  pancreas  may  be  made  which 
shall  have  all  the  power  of  the  natural  juice. 

The  extract  of  the  perfectly  fresh  gland  has  little  or  no  di- 
gestive power. 

The  fully  formed  ferment  does  not  exist  stored  up  in  the 
gland  cells  during  life.  The  living  cells  do  not  contain  trypsin, 
but  hold  an  antecedent  to  this  ferment,  called  zymogen. 

Trypsin  is  quickly  formed  in  the  excised  pancreas  when 
this  is  exposed  to  a  warm  temperature. 

Addition  of  strong  acetic  acid  rapidly  converts  zymogen 
into  trypsin,  and  a  powerful  digestive  fluid  can  then  be  made  by 
extracting  the  gland  with  a  1  p.  c.  solution  of  soda  carbonate. 

THE    RELATION    OF    THE    PROTEID  FERMENTS  OF   THE 
GASTRIC  AND  PANCREATIC  JUICES. 

Gastric  juice  can  digest  only  in  an  acid  medium.  Pancre- 
atic juice  digests  best  in  an  alkaline  fluid,  1  to  2  p.  c.  soda  car- 


—86— 

bonate,  but  is  still  active  in  a  neutral  or  slightly  acid  solution. 
When  pepsin  and  the  pancreatic  ferments  are  mixed  to- 
gether in  an  acid  solution,  pepsin  acts  upon  and  destroys  the 
trypsin. 

THE  STRUCTURE  OF   THE   INTESTINE  AND  THE  SE- 
CRETION PRODUCED  BY  ITS  GLANDS. 

ANATOMY  AND  HISTOLOGY  OF  THE  INTESTINE. 

The  arbitrary  division  of  the  small  intestine  into  duodenum, 
jejunum  and  ileum. 

The  three  coats :  muscular,  areolar,  and  mucous.  The  cir- 
cular and  longitudinal  muscle  fibres. 

The  nerve  plexuses  of  Auerbach  and  of  Meissner. 

The  valvules  conniventes. 

The  villi  of  the  small  intestine  ;  their  capillary  and  lymph 
vessels ;  the  layer  of  muscle  cells ;  the  striated  borders  of  the 
covering  epithelium. 

The  glands  of  Brunner. 

The  "  crypts"  of  Lieberkiihn. 

Peyer's  "  patches." 

The  secretion  of  the  intestinal  glands,  the  Succus  Unteri- 
cus,  is  an  alkaline  fluid  having  slight  proteolytic  and  amylolytic 
digestive  powers. 

THE  BILE. 

The  bile  is  the  secretion  of  the  liver  cells,  and  in  the  inter- 
vals between  digestive  activity  is  stored  up  in  the  gall  bladder. 

CHEMICAL  AND  PHYSICAL  CHARACTERS  OF  BILE. 

The  bile  is  decidedly  alkaline  in  reaction. 

The  green  bile  of  herbivora  and  the  yellow  bile  of  carniv- 
ora. 

The  biliary  pigments  biliverdin  and  bilirubin. 

The  clay  color  of  the  fasces  when  bile  is  prevented  from 
entering  the  intestine. 

Pettenkofer's  test  for  bile  acids. 

The  bile  salts ;  taurocholate  and  glycocholate  of  soda. 

Gmelin's  test  for  bile  pigments. 


—87— 

THE  PROCESS  OF  SECRETION  AND  THE  DIGESTIVE  FUNC- 
TION OF  BILE. 

The  secretion  of  the  bile  increases  rapidly  after  taking  food 
and  reaches  its  maximum  in  -JL  to  10  hours  after  a  meal.  The 
bile,  unlike  the  saliva,  is  secreted  under  a  pressure  much  less 
than  that  of  the  blood. 

The  passage  of  dilute  acid,  as  of  the  contents  of  the  stom- 
ach, over  the  intestinal  orifice  of  the  bile  duct,  causes  a  gush  of 
bile  into  the  intestine  occasioned  by  contraction  of  the  muscles 
of  the  gall  bladder.     This  action  is  purely  reflex. 

If  bile,  or  a  solution  of  bile  salts,  be  added  to  a  fluid  con- 
taining the  products  of  gastric  digestion,  the  complete  and  in- 
complete peptones  in  solution  are  precipitated.  Most  of  the 
pepsin  is  carried  down  mechanically  by  the  precipitate.  Excess 
of  bile  redissolves  the  precipitate  and  the  resulting  solution  is 
alkaline  in  reaction. 

The  precipitation  of  the  dissolved  gastric  peptones  prevents 
their  too  rapid  progress  along  the  intestine,  and  removes  the 
pepsin  whose  action  is  destructive  to  trvDsin. 

Bile  has  a  slight  emulsifying  power  over  fats,  which  is 
much  increased  when  mixed  with  pancreatic  juice. 

Bile  possesses  some  antiseptic  power. 

It  probably  mechanically  assists  in  the  absorption  of  fats, 
as  these  pass  more  readily  through  membranes  moistened  with 
bile. 

Bile  may  furnish  alkali  for  the  formation  of  soaps  in  diges- 
tion. 

Bile  interferes  with  the  process  of  gastric  digestion. 

The  amount  of  bile  secreted  in  24  hours. 

The  effect  of  withdrawing  bile  from  the  body. 

The  history  of  the  food  in  the  small  intestine.     The  chyle, 

ABSORPTION  FROM  THE  SMALL  INTESTINE. 

The  diffusion  of  liquids.     The  absorption  of  fats. 

The  pumping  action  of  the  villi  which  assists  absorption. 

The  diffusion  of  water  through  the  wall  of  the  small  intes. 
tine  is  about  equal  in  both  directions,  for  the  contents  of  the 
ileum  are  as  fluid  as  those  of  the  duodenum.  The  action  of 
purges. 


The  mucous  membrane  of  the  large  intestine  is  crowded 
with  tubular  glands,  but  supports  no  villi. 

The  contents  of  the  large  intestine  rapidly  lose  water  and 
become  dry.  They  become  acid  in  reaction  from  the  products 
of  intrinsic  fermentation.  The  csecal  digestion  of  herbivorous 
animals,  and  its  uses. 

The  gases  found  in  the  large  intestine: — C02,  N,  0H4,  H, 
S  H2. 

The  chemistry  of  the  fasces. 

The  function  of  mucus  as  a  cleanser  of  the  alimentary 
canal. 

THE  MOVEMENTS  OF  THE  INTESTINE. 

Fibres  from  the  vagi  and  splanchnics  unite  the  intestine 
with  the  brain. 

The  peristaltic  contraction  of  the  excised  intestine. 

The  normal  movements  of  the  intestine  and  their  stimulus- 


XVI,   THE  PHYSIOLOGY  OF  NUTRITION. 

The  subject  of  nutrition  is  a  chemical  study,  and  it  has  to 
do  with  the  changes  which  matters  entering  the  living  body 
undergo  there. 

The  waste  matters  of  the  bod}'  are  at  a  lower  chemical 
potential  than  the  food  matters,  and  it  is  believed  that  this 
energy  difference  is  exactly  represented,  by  the  vital  forces  of 
the  animal. 

The  food  matter  absorbed  into  the  body  does  not  necessarily 
fall  directly  to  the  chemical  standpoint  of  the  wastes,  but  it 
probably  most  often  reaches  the  condition  of  the  latter  after 
passing  through  a  series  of  synthetic  as  well  as  analytic 
changes. 

The  products  of  digestion  must  be  worked  over  by  living 
tissues  before  they  form  part  of  the  normal  blood. 

THE  STRUCTURE  OF  THE  LIVER. 

The  liver  is  the  chief  seat  of  changes  undergone  by  the 
digested  food  in  its  preparation  for  the  tissues.  The  blood 
coming  from  this  organ  is  probably  the  warmest  in  the  body. 
In  the  embryo  the  liver  is  proportionately  large,  and  is  there 
probably  the  seat  of  the  formation  of  blood-corpuscles.  In 
many  lower  animals  the  liver  secretes  digestive  juices;  among 
mammals  its  only  secretion,  and  that  is  partly  an  excretion,  is 
bile. 

Most  of  the  blood  of  the  liver  is  collected  from  the  viscera 
into  its  portal  circulation,  from  which  the  circulation  in  the 
hepatic  arteries  and  capillaries  is  distinct. 

The  division  of  the  liver  substance  into  lobules. 

Olisson\3  capsule  and  the  three  interlobular  vessels,  the 
hepatic  artery,  the  portal  vein  and  the  bile  duct,  inclosed  by  it. 
The  intra-lobular,  the  sub-lobular  and  the  hepatic  veins. 

The  hepatic  cells  ;  granular  polyhedral  bodies  often  con- 
taining globules  of  fat  and  masses  of  glycogen. 


—90— 

The  histological  changes  of  the  hepatic  cells  during  diges- 
tion. 

The  origin  of  the  bile  ducts  between  the  liver  cells. 

CONSTRUCTIVE  METABOLISM  OF  THE  BODY. 

THE  PART  PLAYED  BY  THE  LIVER  IN  THE  HISTORY  OF 

GLYCOGEN. 

The  liver  is  preeminently  the  organ  of  those  chemical 
changes  in  the  body  which  do  not  involve  the  formation  or  dis- 
integration of  permanent  tissues. 

Glycogen  may  be  found  in  considerable  quantity  in  the 
liver  cells  of  normal  animals  ;  it  may  also  be  extracted  in  small 
amounts  from  probably  any  living  tissue. 

When  food  is  withheld  from  an  animal  the  quantity  of  gly- 
cogen in  its  liver  begins  immediately  to  diminish,  and  finally 
probably  completely  disappears. 

If  food  be  again  given,  the  accumulation  of  glycogen  in 
the  liver  proceeds  rapidly  till  it  has  reached  its  former  amount. 
Carbohydrate  foods  are  particularly  favorable  to  the  laying  up 
of  glycogen  by  the  liver. 

The  glycogen  is  no  doubt  constructed  by  the  activity  of  the 
liver  cells  out  of  the  food  matter  coming  from  the  digestive 
tract. 

When  the  liver  is  removed  from  the  body  and  allowed  to 
lie  in  a  warm  place,  after  a  time  it  is  found  that  the  glycogen 
has  disappeared  and  that  sugar  has  been  produced  in  its  place. 
If  the  liver  be  boiled  while  quite  fresh,  it  is  found  to  contain 
much  glycogen  but  little  or  no  sugar.  When  the  liver  is  re- 
moved from  the  body  its  store  of  glycogen  is  turned  into  sugar 
by  the  action  of  a  ferment,  probably  produced  within  the  liver 
cells. 

It  is  probable  that  the  glycogenetic  function  of  the  liver 
consists  in  the  storage  within  the  liver  cells  of  the  carbohy- 
drate moieties  of  the  food  matter  in  the  comparatively  insolu- 
ble form  of  glycogen.  Under  normal  conditions  this  glycogen 
is  transformed  into  soluble  sugar  at  a  certain  definite  rate,  the 
sugar  passing  into  the  general  circulation  for  the  supply  of  the 
tissues.      Through   this   function  of  the  liver,  both  the  over- 


—91— 

loading  of  the  tissues  with  carbolrydrate  matter  at  the  time  of 
feeding  and  their  suffering  for  want  of  it  in  time  of  hunger,  are 
prevented. 

Reasons  for  believing  that  proteid  food  matters  give  rise  to 
carbohydrates  in  the  liver. 

DIABETES. 

Temporary  diabetes  may  be  artificially  produced  in  an 
animal.  If  a  well-fed  rabbit  be  punctured  in  the  vaso-motor 
region  of  the  medulla  the  flow  of  the  urine  will  be  increased 
and  in  one  to  two  hours  it  will  contain  considerable  sugar, 
which  after  a  day  or  two  will  have  disappeared  again.  If  the 
animal  be  previously  starved  so  that  the  liver  contains  little 
or  no  glycogen,  the  urine  after  the  operation  will  contain  little 
or  no  sugar.  The  sugar  found,  then,  has  come  from  stored-up 
glycogen. 

The  obscurity  of  the  cause  of  this  diabetes. 

Mild  and  severe  forms  of  natural  diabetes  and  the  relation 
of  the  nature  of  the  food-supply  to  them. 

FOBMATION  OF  FAT  IN  THE  BODY. 

The  fluctuation  in  the  quantity  of  fat  in  the  body. 

Histological  changes  in  the  connective  tissue  corpuscle 
which  is  being  converted  into  a  fat  cell. 

Fatty  degeneration  of  proteid-containing  tissues. 

The  ripening  of  cheese. 

The  fat  of  the  body  may  be  produced  from  the  metabolism 
of  food  matters  other  than  fat.  A  greater  quantity  of  fat  may 
appear  in  the  milk  of  a  cow  than  was  contained  in  the  food  of 
the  animal.  The  amount  of  wax  produced  by  bees  far  exceeds 
that  of  the  fat  found  in  the  saccharine  food  of  the  creatures. 
It  has  been  shown,  in  one  instance,  that  for  every  100  parts  of 
fat  in  the  food  of  a  fattening  pig,  472  parts  were  laid  up  as  fat 
in  the  body. 

Proteid  foods  as  a  source  of  fat. 

The  fat  of  the  living  body  consists  of  certain  average  pro- 
portions of  trio-olein,  tri-palmitin  and  tri-stearin,  which  are 
unaltered  by  the  variation  of  the  proportions  of   those  sub- 

12 


—92— 

stances  in  the  food  ;  therefore  the  fat  of  the  body  is  not  simply 
that  of  the  food  stored  up  unchanged. 

The  chemical  changes  by  means  of  which  carbohydrates 
and  proteids  may  give  rise  to  fats. 

THE    STRUCTURE   AND  SECRETION   OF    THE  MAMMARY 

GLANDS. 

Each  human  mammary  gland  is  composed  of  a  number  of 
distinct  lobes  which  are  bound  together  by  connective  tissue 
containing  much  fat.  Each  lobe  is  farther  divided  into  smaller 
and  smaller  lobules.  The  ductules  of  neighboring  acini  unite, 
and  the  ducts,  from  15  to  20  in  number,  of  the  various  lobes 
thus  formed  open  separately  upon  the  nipple.  The  ducts  are 
dilated  near  their  external  openings  so  as  to  form  small  milk 
reservoirs.  The  ducts  and  the  terminal  acini  are  lined  by  short 
columnar  epithelium. 

Fresh  milk  is  alkaline  in  reaction  but  may  become  acid 
while  yet  in  the  gland  duct.  Its  chemical  constituents  are, — 
water ;  casein,  serum  albumin  ;  fats ;  milk  sugar ;  potassium 
phosphate,  calcium  phosphate,  potassium  chloride,  magnesium 
phosphate. 

The  fatty  globules  forming  the  emulsion  are  surrounded  by 
albuminous  envelopes. 

Colostrum  differs  from  ordinary  milk  in  being  deficient  in 
casein  and  proportionately  rich  in  albumin. 

Milk  sugar  is  readily  changed  by  fermentation  into  lactic 
acid,  which  then  causes  coagulation  of  the  casein. 

The  protoplasm  of  the  mammary  gland  cell  probably  forms 
all  the  organic  constituents  of  the  milk. 

Histological  changes  in  the  gland  cells  during  lactation. 

The  fats  of  milk  are  increased  by  proteid  feeding  and  the 
amount  of  milk  sugar  is  not  dependent  on  the  carbohydrates 
eaten. 

The  ferment  secreted  by  the  stomach  glands  which  coagu- 
lates casein. 

THE  STRUCTURE  AND  PHYSIOLOGY  OF  THE  SPLEEN. 

The  structure  of  the  spleen  is  much  like  that  of  a  lym- 


—93— 

phatic  gland.  The  organ  consists  of  a  reticular  framework  of 
bands  of  elastic  tissue,  in  the  interspaces  of  which  rests  the  red- 
brown  spleen  pulp  which  consists  of  a  network  of  branched 
connective  tissue  corpuscles,  through  the  interstices  of  which 
oozes  blood  in  which  are  found  red  corpuscles  apparently 
undergoing  destructive  metamorphosis.  The  trabecular  sub- 
stance of  the  spleen  contains  much  plain  muscular  tissue. 
The  outer  connective  tissue  coat  of  the  smaller  arteries  is 
frequently  dilated  into  small  spheroidal  bodies  which  have 
the  structure  of  lymph  follicles,  the  so  called  Malpighian 
corpuscles. 

The  spleen  may  be  extirpated  without  danger  to  the  life  of 
the  animal.  After  such  an  operation  there  seems  to  be  an  in- 
crease in  the  size  of  the  lymphatic  glands  and  in  the  activity 
of  the  red  medulla  of  bones. 

The  spleen  increases  in  size  up  to  about  the  fifth  hour  of 
digestion,  and  then  diminishes  again. 

The  amount  of  blood  passing  through  the  spleen  is  proba- 
bly regulated  by  the  action  of  the  muscle  fibres  found  in  the 
trabecular  tissue  of  the  organ.  Rhythmic  contractions  of  the 
spleen. 

The  spleen  is  probably  a  seat  of  the  formation  of  white 
corpuscles  and  destruction  of  red  corpuscles  of  the  blood.  The 
peculiar  "  spleen  corpuscles  "  which  contain  fragments  of  red 
blood  disks. 

The  pulp  of  the  spleen  is  very  rich  in  so-called  extractive 
matters. 

THE  ORIGIN  OF  UREA. 

The  living  tissues  are  continually  being  wasted  and  re- 
stored, and  the  nitrogen  of  the  wastes  is  nearly  all  contained 
in  the  urea  excreted. 

Muscular  tissue  contains  kreatin,  uric  acid  and  other  crys- 
taline  nitrogenous  bodies,  but  no  urea. 

THE  RELATION  OF  THE  KIDNEYS  TO   THE    FORMATION 

OF  UREA. 

It  is  probable  that  the  nitrogenous  crystalline  substances 


—94— 

of   muscle    are  waste  products   of    the   tissue   and    in    part 
antecedents  of  urea. 

There  is  some  reason  to  believe  that  the  cells  of  the  renal 
tubules  may  effect  the  conversion  into  urea  of  certain  antece- 
dents of  the  latter  which  are  found  in  the  blood. 

THE  RELATION  OF  PANCREATIC  DIGESTION  AND  OF  THE 
LIVER  TO  THE  FORMATION  OF  UREA. 

The  pancreatic  digestion  of  proteids  may  give  rise  in  the 
intestine  to  considerable  amounts  of  leucin  and  tyrosin. 
Leucin  injected  into  the  alimentary  canal  reappears  as  urea  in 
the  urine.  The  liver  always  contains  urea  in  its  substance.  It 
is  not  improbable  that  the  liver  cells  turn  into  urea  the  leucin 
produced  by  excessive  proteid  digestion  in  the  intestine. 

The  possible  chemical  process  by  which  the  liver  forms 
urea  from  leucin,  as  indicated  by  the  results  which  follow  the 
ingestion  of  sarcosin. 

Increase  of  proteid  in  the  food  increases  the  amount  of 
urea  excreted.  It  is  probable  that  the  amount  of  leucin  and 
tyrosin  formed  in  pancreatic  digestion  is  proportional  to  the  ex- 
cess of  proteid  in  the  food. 

Uric  acid,  though  less  oxidized  than  urea,  is  probably  not 
an  antecedent  of  the  latter.  Uric  acid  replaces  the  urea  in  the 
excrement  of  birds. 

The  chemical  functions  of  the  liver  which  are  indicated  in 
the  elimination  of  hippuric  acid. 

STATISTICAL  STUDY  OF  NUTRITION. 

The  proportion  in  which  the  various  tissues  exist  in  the 
body.     The  relative  diminution  of  the  tissues  during  starvation. 

The  history  of  nitrogen  excretion  in  the  urine  of  a  starving 
animal.     Luxus  consumption. 

The  study  of  the  changes  taking  place  in  the  body  by  a 
comparison  of  the  substances  entering  it  with  those  coming  out 
of  it. 

The  effect  of  nitrogenous  foods  on  the  chemical  processes 
of  the  body.     Nitrogen  equilibrium. 

The  Banting  system  of  dietetics. 


^95— 

The  effects  of  fatty,  of  carbohydrate  food,  and  of  gelatine. 

The  function  of  these  foods  as  force  regulators. 

The  effects  of  salts  in  the  food. 

It  is  probable  that  the  urea  excreted  has  at  least  two  differ- 
ent sources ;  arising  in  pretty  definite  quantities  from  the  nitro- 
genous tissues,  and  also  coming  in  fluctuating  quantities  from 
the  decomposition  of  proteid  matter  which  never  forms  part  of 
the  general  tissues. 

The  dietetic  value  of  the  various  food  stuffs. 

THE  NATURE  OF  THE  PROCESSES  WHICH  GIVE  RISE 
TO  THE  BODILY  ENERGY. 

The  amount  of  energy  evolved  by  the  body  is  represented 
by  the  difference  between  the  chemical  potentials  of  the  food 
and  the  waste  matter,  and  is  wholly  unaffected  by  the  manner 
in  which  this  degradation  is  brought  about. 

In  every  change  of  matter  in  the  body  by  which  molecules 
are  made  more  unstable,  energy  is  absorbed ;  in  every  change 
in  which  the  reverse  takes  place,  energy  is  evolved. 

The  energy  set  free  in  the  body  all  reappears  either  as  heat 
or  mechanical  energy. 

Those  movements  of  the  body  which  involve  friction  are 
attended  with  a  loss  of  heat.  The  difference  between  the 
mechanical  energy  of  the  blood  in  the  aorta  and  in  the  vense 
cavae  must  be  represented  by  an  equivalent  of  heat,  produced 
by  friction  in  the  blood-vessels.  The  heat  lost  by  radiation, 
conduction  and  evaporation  owes  its  origin  to  chemical  changes 
in  the  body. 

THE  ENERGY  SUPPLY  OF   THE  BODY. 

The  amount  of  energy  stored  up  in  the  various  food  matters 
may  be  determined  in  heat  units  when  they  are  completely 
burned. 

The  direct  oxidation  of  the  following,  Gives  rise  to 

dried  at  100°  Centigrade  :  Gram,  degree.        Met. -Kilo. 

1  gram  Beef-fat 9069  3841 

1  gram  Arrowroot 3912  1657 

1  gram  Beef-muscle  purified  with  ether  _  5103  2161 

1  gram  Urea 2206  934 


—96— 

Supposing  that  all  the  nitrogen  of  proteid  food  goes  out  as 
urea,  1  gram  of  dry  proteid,  such  as  dried  beef-muscle,  would 
give  rise  to  about  one-third  gram  of  urea,  hence  : 

Gram,  degree.  Met.-Kilo- 

1  gram  Proteid 5103  2161 

Less 

-}  gram  Urea 735  331 

Available  energy  of  1  gram  of  Proteid —  4368  1850 

(Foster's  Physiology.) 

THE  SOURCE  OF  ENERGY  OF  MUSCULAR  WORK. 

It  was  the  belief  of  Liebig  that  the  non-nitrogenous,  or 
"  respiratory,"  foods  were  oxidized  in  the  body  to  maintain  its 
temperature,  while  the  nitrogenous,  or  "  plastic,"  foods  went  to 
form  the  living  tissues,  and  that  the  functional  changes  of  the 
latter  gave  rise  to  the  nitrogen  of  the  egesta. 

It  is  probable  that  muscular  labor  does  not  involve  the 
destruction  of  the  nitrogenous  part  of  the  muscle  molecule. 
The  amount  of  nitrogen  excreted  is  not  increased  by  muscular 
work . 

The  experiments  of  Parkes,  of  Fick  and  Wislicenus.  The 
experiments  of  Flint. 

The  amount  of  carbonic  acid  excreted  is  immediately  and 
greatly  increased  by  muscular  work. 

The  experiments  of  Pettenkofer  and  Voit  comparing  the 
oxidations  of  the  body  while  in  a  state  of  rest  and  at  work. 

The  oxidations  of  the  body  occur  in  the  tissues  and  not  in 
the  blood  or  the  lungs.  These  oxidations  are  not  immediately 
dependent  upon  the  respiration.  Excess  of  carbonic  acid  given 
off  daring  the  day  and  of  oxygen  absorbed  in  the  night. 

The  muscle  molecule  probably  consists  of  an  essential 
nitrogenous  portion  capable  of  adding  to  itself  certain  combus- 
tible non-nitrogenous  matters,  which  latter,  during  functional 
activity,  are  oxidized  and  give  rise  to  free  energy.  It  is  proba- 
ble, however,  that  the  whole  molecule  takes  part  in  such  a  de- 
structive change. 

ANIMAL  HEAT. 

The  energy  difference  between  the  food  and  waste  matters 


—97— 

all  reappears  as  heat  in  a  resting  animal.  During  work,  the 
oxidations  of  the  body  and  the  heat  produced  are  increased. 

The  muscles,  glands  and  central  nervous  tissues  are  the 
chief  seats  of  heat  production  in  the  body. 

The  mechanical  energy  of  the  circulating  blood  finally  re- 
appears as  heat. 

The  body  temperature  of  different  animals.  Cold-blooded 
and  warm-blooded  animals.  The  temperature  of  hibernating 
animals. 

The  difference  between  the  temperatures  of  different  parts 
of  the  body  and  the  variation  of  the  temperature  in  the  same 
part. 

The  daily  variation  of  the  body  temperature. 

The  blood  coming  from  the  liver  is  the  warmest  in  the 
body. 

The  blood  as  a  heat  distributer. 

The  temperature  of  the  body  depends  upon  the  ratio  of 
heat  production  to  heat  dissipation. 

THE  MAINTENANCE   OF   A   CONSTANT   BODY  TEMPERA- 
TURE. 

THE   REGULATION  OF   THE   LOSS   OP   HEAT. 

The  loss  of  heat  through  various  channels  is  calculated  as 
follows : 

In  warming  fseces  and  urine 2.5  p.  c. 

In  warming  expired  air 5.2  p.  c. 

In  evaporating  the  water  of  respiration--  14.7  p.  c. 
In  conduction,  radiation  and  evaporation 

by  the  skin 77.5  p.  c. 

The  means  by  which  the  loss  of  heat  through  the  lungs  and 
skin  is  controlled. 

The  reflex  excitement  of  the  organs  through  which  heat  is 
lost  to  the  body.    Temperature,  nerves.     Heat  dyspnoea. 

The  perfection  of  this  regulation  as  shown  by  the  high 
temperatures  which  can  be  borne  in  a  dry  atmosphere. 

In  some  hair-covered  animals  the  chief  loss  of  heat  is  by 
means  of  the  lungs  and  mouth. 

The  function  of  the  non-conducting  layer  of  subcutaneous 
fat. 


—98— 
THE  REGULATION  OF  HEAT  PRODUCTION. 

The  oxidations  in  the  body  of  a  warm-blooded  animal  are 
increased  by  a  low  surrounding  temperature;  those  of  a  cold- 
blooded animal  are  decreased. 

This  increased  production  of  heat  in  warm-blooded  animals 
is  probably  the  result  of  a  reflex  action  in  which  the  activity  of 
a  thermogenic  nerve-centre  is  involved.  A  curarized  animal, 
or  one  whose  spinal  cord  has  been  divided,  shows,  like  a  cold- 
blooded creature,  diminished  oxidations  when  the  surrounding 
temperature  is  lowered. 

The  action  of  a  thermogenic  centre  increases  the  chemical 
changes  of  the  tissues,  leading  to  an  excessive  absorption  of 
oxygen  and  evolution  of  carbonic  acid. 

It  has  been  made  certain  that  the  loss  of  heat  from  the 
body  is  under  nervous  control,  chiefly  through  means  of,  1,  the 
vasomotor  centres;  2,  the  sweat  centres;  3,  the  respiratory 
centres. 

It  has  been  made  highly  probable  that  the  production  of 
heat  is  under  the  nervous  control  of  centres  which  cause,  1,  an 
increase  of  heat  production ;  2,  a  diminution  of  heat  produc- 
tion. That  is,  there  are  probably  heat  producing  and  heat  in- 
hibitory nerve- centres. 

THE  INFLUENCE  OF  THE  NERVOUS  SYSTEM  ON  THE 
NUTRITIVE  PROCESSES  OF  THE  BODY. 

Many  obscure  facts  point  to  a  nervous  regulation  of  the 
nutritive  processes  of  the  body,  but  in  no  instance  has  such 
an  action  been  proven.  Inflammation  of  the  cornea  which 
follows  section  of  the  trigeminal  nerve.  Pneumonia  which 
succeeds  division  of  the  vagi. 

The  chemical  action  of  the  sympathetic  nerves  on  the  pa- 
rotid gland.  Gaskell's  theory  of  anabolic  and  katabolic  nerve 
action. 

It  is  at  present  safest  to  consider  that  the  healthy  nutrition 
of  a  part  depends  upon  the  sum  total  of  its  physiological 
actions  rather  than  on  the  influence  exerted  by  a  special 
"  trophic  "  nerve. 


XVII.   THE  SPINAL  CORD, 

STRUCTURE  OF  THE  SPINAL  CORD  AND'ACCESSORY 

PARTS. 

The  spinal  cord  is  closely  invested  by  the  vascular  pia 
mater,  which  gives  rise  to  the  connective  tissue  frame-work  of 
the  cord. 

Outside  the  pia  mater  is  the  arachnoid  membrane,  and  be- 
tween the  two  sheets  of  tissue  is  found  the  cerebro-spinal  fluid. 
The  functions  of  the  cerebro-spinal  fluid. 
Surrounding  the  parts  just  described  is  a  dense  membrane, 
the  dura  mater,  which  is,  at  points,  attached  to  the  wall  of  the 
neural  canal. 

The  spinal  cord  is  held  in  position  by  the  spinal  nerves 
entering  it,  and  by  ligaments  passing  from  the  pia  mater  to  the 
dura  mater. 

The  cervical  and  lumbar  enlargements  of  the  cord. 
The  cauda  equina  and  the  Mum  terminate. 
Each  spinal  nerve  divides  into  two  branches,  the  anterior 
and  posterior  spinal  roots,  just  after  entering  the  neural  canal. 
All  the  sensory  fibres  of  the  spinal  nerves  enter  the  cord  by 
the  posterior  roots  ;  all  the  motor  fibres  leave  the  cord  by  the 
anterior  roots.  Each  posterior  root  bears  a  ganglion  near  the 
point  of  its  juncture  with  the  anterior  root. 

The  function  of  the  ganglion  of  the  posterior  nerve-root. 
The  spinal  cord  is  divided  longitudinally  on  its  anterior 
side  by  a  broad  shallow  groove,  the  anterior  median  -fissure 
Posteriorly  the  cord  is  similarly  divided  by  a  deeper  and  nar- 
rower posterior  median  -fissure,  which  is  filled  by  a  sheet  of 
inflected  connective  tissue.  The  two  sets  of  spinal  nerve  roots 
enter  the  cord  along  tolerably  definite  lines,  the  lateral  fissures. 
As  marked  out  by  these  fissures,  the  cord  may  be  considered  to 
be  made  up  of  a  pair  of  anterior,  a  pair  of  lateral,  and  a  pair 
of  posterior  columns.  The  posterior  columns  have  further  in- 
dicated on  their  surface  a  narrow  posterior  median  column. 
13 


—100— 

The  central  canal  of  the  spinal  cord,  lined  by  cuboidal 
ciliated  epithelium. 

Running  through  the  cord  is  a  core  of  gray  matter  which 
has  a  double  crescent  shape  in  cross-section. 

Distribution  of  the  nerve  cells  in  the  gray  matter.  Golgi's 
views  on  the  structure  of  nerve  cells. 

The  nervous  matter  of  the  white  substance  of  the  cord  is 
composed  of  medullated  nerve  fibres ;  that  of  the  gray  sub- 
stance is  made  of  nerve  cells,  and  nerve  fibres  chiefly  without 
the  fatty  sheath. 

The  variation  in  form  and  mass  of  the  gray  matter  in  dif- 
ferent parts  of  the  cord.  The  gelatinous  substance  in  the  pos- 
terior cornua. 

The  shape  and  distribution  of  the  nerve  cells  and  the  con- 
nection of  nerves  with  them. 

The  anterior  white  commissure  and  the  gray  commis- 
sures. 

Most,  if  not  all,  the  nerve  fibres  reaching  the  spinal  cord, 
sooner  or  later  enter  its  gray  substance. 

The  nervous  elements  of  the  cord  are  intimately  bound  to- 
gether and  supported  by  a  connective  tissue  frame-work.  The 
neuroglia. 

THE  SPINAL  CORD  AS  A  CENTRE  FOR  REFLEX 
ACTIONS. 

The  spinal  cord  contains  nervous  centres  capable  of  send- 
ing out  nervous  discharges  which  may  stir  up  complicated, 
co-ordinated,  and  adaptive  movements. 

These  movements  are  never  initiated  in  the  cord,  but  are 
brought  about  by  impulses  reaching  the  cord  from  without ; 
that  is,  they  are  not  spontaneous,  but  reflex  in  character. 

* 

Automatic  centres  controlling  organic  functions,  however, 
no  doubt  exist  in  the  spinal  cord. 

The  stimulation  of  the  terminal  organs  of  the  afferent 
nerves  is  much  better  adapted  for  arousing  reflexes  than  the 
direct  stimulation  of  a  nerve  trunk.  , 

The  nerve  cell  requires  time  to  cause  an  efferent  nervous 
discharge  after  having  received  an  impulse  from  an  afferent 


—101 — 

nerve.  The  reflex  nerve  cell  is  readily  excited  to  action  by  a 
succession  of  distinct  impulses  reaching  it,  but  rarely  by  a 
single  one. 

Extremely  feeble  stimuli  when  summated  in  the  spinal 
cord  may  produce  powerful  effects.    Examples. 

The  inhibition  of  a  reflex  action  may  be  occasioned  by  the 
strong  stimulation  of  any  afferent  nerve,  or  by  the  influence  of 
nerve  centres  in  the  brain  or  spinal  cord  other  than  the  reflex 
centre. 

The  physiological  nature  of  "  shock." 

The  spinal  cord  has  no  power  of  learning  to  adapt  its  activ- 
ities to  new  conditions. 

In  a  certain  sense  the  spinal  cord  may  be  looked  on  as  a 
servant  of  the  centres  of  intelligence  which  has  learned,  under 
their  instruction,  to  carry  out  alone  certain  oft  repeated 
actions. 

There  is  no  evidence  of  the  spinal  cord  possessing  a  con- 
scious intelligence. 

THE    SPINAL    CORD    AS   A  COLLECTION   OF   AUTO- 
MATIC CENTRES. 

One  of  the  functions  of  the  spinal  cord,  probably,  is  to  act 
nearly  independently  by  means  of  special  centres  whose  duty 
it  is  to  preserve  the  organic  welfare  of  the  body,  and  whose 
powers  in  part  are,  no  doubt,  automatic.  The  nervous  control 
of  the  sphincter  muscles  of  the  body ;  the  sexual  centres  ; 
muscular  tonicity  ;  subsidiary  vaso-motor  centres. 

The  peculiar  movements  of  a  mammal  with  divided  spinal 
cord. 

THE  PATHS  OF  CONDUCTION  IN  THE  SPINAL  CORD. 

We  usually  have  conscious  sensation  of  the  impulses  reach- 
ing the  spinal  cord ;  in  such  cases  the  impulses  must  have  been 
transmitted  to  the  brain. 

We  cannot  suppose  that  all  the  nerve  fibres  entering  the 
cord  are  individually  represented  by  fibres  passing  to  the  brain 
in  that  organ,  for  the  number  of  nerve  fibres  in  the  spinal 
cord  is  not  great  enough  to  admit  of  this.    In  such  a  case, 


—102— 

also,  the  shape  of  the  spinal  cord  would  be  that  of  an  inverted 
cone. 

We  may  suppose  that  the  fibres,  or  most  of  them,  from  the 
periphery  on  the  one  hand,  and  from  the  brain  on  the  other, 
are  connected  with  certain  nerve  centres  in  the  gray  matter  of 
the  spinal  cord  by  whose  mediation  impulses  reaching  the  cord 
from  many  different  sources  may  be  sent  out  of  it  by  a  single 
channel,  or  conversely.  In  this  sense  the  nerve  centres  of  the 
cord  act  as  relay  stations  for  the  transmission  of  impulses 
reaching  them  from  any  quarter. 

.  The  segmental  distribution  of  the  gray  matter  in  the  cord. 
The  area  of  gray  matter  in  a  cross  section  of  the  cord  rises 
and  falls  with  the  sectional  area  of  the  nerve  fibres  entering 
the  cord  at  that  level. 

It  has  been  attempted  to  determine  the  anatomical  and 
physiological  grouping  of  the  nerve  fibres  of  the  spinal  cord, 

(1)  by  a  study  of  the  direction  in  which  cut  fibres  degenerate ; 

(2)  by  the  different  periods  at  which  various  collections  of  the 
fibres  assume  the  medullary  sheath  ;  (3)  by  pathological  data ; 
(4)  by  observation  of  the  results  following  physiological  ex- 
periment. 

Differentiation  of  the  parts  of  a  cross  section  of  the  spinal 
cord.  In  the  white  matter  the  columns  of  Tiirck,  of  Burdach 
and  of  Goll ;  the  anterior  and  the  lateral  pyramidal  tracts  ;  the 
direct  cerebellar  tracts.  In  the  gray  matter,  the  groups  of  cells 
in  the  anterior  and  posterior  cornua,  and  the  column  of  Clark. 

All  impulses,  whether  sensory  or  motor,  passing  between 
the  brain  and  the  body  at  large,  cross  the  middle  line  and  end 
in  the  side  opposite  to  that  in  which  they  originated. 

The  decussation  occurs  at  the  level  of,  and  below  the  pons 
varolii. 

Sensory  impulses  probably  cross  to  the  opposite  side  lower 
down  in  the  spinal  cord  than  do  the  volitional  impulses. 

Volitional  impulses  cross  most  largely  in  the  medulla  and 
travel  along  the  cord  in  the  lateral  and  anterior  columns,  and 
enter  the  nervous  centres  of  the  anterior  cornua  of  the  gray 
matter  of  the  cord,  whence  they  emerge  in  the  anterior  spinal 
roots.  Volitional  fibres  which  have  not  already  crossed  to  the 
opposite  side  in  the  medulla  probably  pass  down  the  cord  in 


—loa- 
the anterior  column  on  the  same  side  as  that  on  which  they 
originate,  until  they  cross  the  middle  line  and  then  enter  the 
lateral  column  of  the  opposite  side.  Usually  from  90  to  9*  per 
cent,  of  the  volitional  fibres  cross  at  the  decussation  of  the 
pyramids,  but  occasionally  the  proportion  is  reversed.  In- 
stances are  recorded  of  direct  cerebral  paralysis. 

Sensory  impulses  reaching  the  cord  enter  the  posterior 
cornua  of  it  gray  matter  or  its  posterior  white  column-,  and 
soon  crossing,  proceed  to  the  brain  chiefly  in  the  lateral  col- 
umns. 

Tracts  of  degeneration  in  the  spinsl  cord  accompanying 
various  forms  of  paralysis. 

The  most  marked  results  of  lateral  hemi- section  of  the 
spinal  cord  is  a  paralysis  of  voluntary  motion  and  hyperes- 
thesia on  the  same  side  below  the  injury,  with  a  loss  of  sen- 
sation on  the  opposite  side:  probably  neither  of  these  effects  is 
complete. 

The  functions,  sensory  and  motor,  which  are  abolished  by  a 
hemi-section  of  the  cord  may  be  gradually  recovered  without 
reunion  of  the  divided  parts. 

.  The  teachings  of  pathological  lesions   of  various  parrs  of 
the  spinal  cord. 

Purely  tactual  and  painful  sensory  impulses  probably  pass 
through  the  cord  along  different  paths.  The  phenomena  of 
analgesia. 

The  gray  matter  of  the  cord  can.  no  doubt,  conduct  in  any 
direction  the  impulses  which  reach  it. 


XVIII.   THE  BRAIN. 

THE  MEDULLA  OBLONGATA. 

The  medulla,  besides  being  the  pathway  of  the  nerve  fibres 
connecting  the  brain  and  spinal  cord,  contains  a  number  of 
automatic  and  reflex  nerve  centres  which  especially  preside 
over  the  "  organic  "  functions  of  the  body.  Among  the  nerve 
centres  are  included, — a  respiratory  centre  ;  a  cardio-inhibitory 
centre ;  a  diabetic  centre  ;  a  vaso-motor  centre ;  centre  of  deglu- 
tition ;  centre  for  reflex  secretion  of  saliva  ;  a  vomiting  centre  ; 
centre  for  movements  of  oesophagus  and  stomach;  and  prob- 
ably centres  for  the  co-ordination  of  movements  of  the  body. 

The  medullary  centres,  though  capable  of  independent 
action,  are  no  doubt  normally  under  the  influence  of  other  sim- 
ilar centres  in  higher  parts  of  the  brain. 

THE   CHANGES   PRODUCED  IN  AN  ANIMAL  BY  THE 
REMOVAL  OF  ITS  CEREBRUM. 

A  frog  or  a  pigeon  bears  well  the  extirpation  of  the  cere- 
brum, but  a  mammal  sooner  or  later  succumbs  to  such  an  oper- 
ation. 

The  loss  of  the  cerebrum  involves  the  loss  of  spontaneous 
movement ;  an  animal  without  that  organ  stirs  only  in  answer 
to  a  stimulus. 

With  the  loss  of  its  cerebrum  an  animal  appears  to  lose  its 
faculty  of  perception  and  the  power  of  forming  judgments. 
The  deterioration  of  the  animal  is  in  its  psychical  powers. 

Definitions  of  sensation,  perception  and  judgment. 

The  aspects  of  a  frog  and  of  a  pigeon  after  removal  of  the 
cerebral  lobes  are  nearly  normal.  Food  is  not  voluntarily  taken, 
though  it  is  swallowed  when  placed  in  the  mouth.  No  sign  of 
fear  can  be  aroused.  The  animal  exhibits  no  further  evidence 
of  the  possession  of  free  will. 

The  most  complex  co-ordinated  movements  may  still  be 


—106— 

carried  out.  The  balancing  and  swimming  of  a  frog,  and  the 
flight  of  a  pigeon  whose  cerebral  hemispheres  have  been  re- 
moved. Such  an  animal  appears  to  retain  its  normal  sensa- 
tions. A  frog  deprived  of  its  cerebrum  avoids  obstacles  in 
leaping. 

The  same  general  results  follow  the  destruction  of  the 
cerebrum  in  a  mammal.  A  rabbit  or  a  rat  so  treated  ceases  to 
notice  food.  Its  gaze  is  attracted  by  a  moving  light,  and  it 
may  utter  plaintive  cries  and  leap  on  being  stimulated.  Its 
sensations  are  preserved  but  it  preceptions  are  lost. 

Relation  of  the  weight  of  the  brain,  the  number  of  its  con- 
volutions and  the  depth  of  its  fissures  to  animal  intelligence. 

THE  LOCALIZATION  OF  FUNCTION  IN  THE 
CEREBRUM. 

THE  STRUCTURE  OF  THE  CEREBRUM. 

The  interior  of  the  cerebral  hemispheres  is  chiefly  com- 
posed of  masses  of  nerve  fibres  which  terminate  in  the  cortex. 
The  nerve  cells  of  the  cerebrum  are  contained  in  the  cortical 
substance,  a  thin  sheet  of  gray  matter  which  overlies  the  con- 
voluted surface  of  the  hemispheres. 

In  general,  the  cerebrum  may  be  considered  to  be  the  seat 
of  thought,  of  consciousness,  and  of  will  power. 

It  is  not  certain  whether  the  manifold  functions  of  the 
cerebral  cortex  are  separately  localized  in  the  various  convolu- 
tions, or  whether  the  whole  brain  is  to  be  regarded  as  a  com- 
plicated machine  in  which  the  activity  of  one  part  involves 
that  of  all  the  rest. 

The  effect  of  gradual  removal  of  a  pigeon's  brain  is  a 
gradual  loss  of  physical  power  in  the  animal. 

In  certain  pathological  conditions,  as  in  the  disease  aphasia, 
there  is  strong  suggestion  of  a  localization  of  function  in  the 
cortex.  The  3d  frontal  convolution,  the  seat  of  disease  in 
aphasia,  seems  to  be  best  developed  in  intelligent  persons. 

The  limited  anastomosis  of  the  blood  vessels  of  the  cortex 
is  suggestive  of  localization. 

There  may  be  produced  in  an  animal  definite  movements 
or  signs  of  sensation,  as  a  result  of  the  electrical  stimulation  of 


—107— 

well  defined  areas  of  the  cerebral  convolutions.  Mechanical 
or  chemical  stimulation  of  the  cortex  is  not  followed  by  posi- 
tive results. 

The  different  results  following  stimulation  of  the  cortex  in 
the  various  stages  of  morphia  narcosis. 

Removal  of  a  "  motor  "  area  of  the  cortex  is  said  by  some 
to  be  followed  by  a  loss  of  voluntary  control  over  the  muscles 
formerly  excited  by  the  stimulation  of  that  area.  Destruction 
of  the  motor  areas  on  one  side  of  the  cortex  produces  perman- 
ent paralysis  of  the  opposite  side  of  the  body  in  the  monkey, 
but  the  paralysis  is  temporary  in  the  dog.  Removal  of  a  "sen- 
sory" area  is  said  in  like  manner  to  involve  a  loss  of  the  appro- 
priate sensations. 

The  results  supporting  the  theory  of  localization,  as  ob- 
tained in  the  experiments  of  Fritsch  and  Hitzig,  of  Ferrier  and 
of  Munk. 

The  nature  of  the  phenomena  brought  out  by  artificial 
stimulation  of  the  cortex,  and  of  those  which  follow  the  extir- 
pation of  various  areas. 

There  is  a  gradual  recovery  from  the  motor  paralysis  or 
loss  of  sensation  which  follows  removal  of  a  limited  area  of  the 
cortex. 

In  this  recovery  the  function  of  the  lost  part  has  not  been 
assumed  by  any  definite  homologous  area  in  another  part  of 
the  brain. 

Extensive  lesions  of  the  brain  have  been  suffered  by  men 
without  permanent  motor  or  sensory  disturbance. 

According  to  the  experiments  of  Goltz,  there  is  no  distinct 
localization  of  function  in  the  cerebral  cortex;  but  a  gradual 
loss  of  psychical  power,  of  sensation,  and  of  definite  volun- 
tary motion,  follows  extirpation  of  any  part  of  the  cerebral 
convolutions  in  the  dog,  and  these  disturbances  are  more  ex- 
tensive and  less  readily  recovered  from,  the  more  widespread 
the  lesion. 

After  suffering  from  an  operation  an  animal  responds  in  a 
reflex  manner  to  stimuli  much  more  readily  than  usual. 

Exaggeration  of  the  "  tendon  reflex  "  in  motor  volitional 
paralysis. 

Parts  of  the  brain  below  the  cerebrum  are  no  doubt  capable 
14 


—108— 

of  carrying  out  independently  complicated  activities  in  which 
simple  sensations  are  involved. 

The  difference  between  psychoses  and  neuroses. 

Cerebral  "  reaction  time."  Average  reaction  times  for  the 
different  senses  in  fractions  of  a  second : — feeling,  1-7 ;  hear- 
ing, 1-6  ;  sight,  1-5.    Reduced  reaction  time  1-10. 

THE  CORPORA  STRIATA  AND  THE  OPTIC  THALAMI. 

The  so-called  "  basal  ganglia  "  are  masses  of  gray  tissue 
containing  many  nerve  cells.  Most  of  the  fibres  of  the  crura 
cerebri  pass  into  the  basal  ganglia  before  proceeding  to  the 
cortex  of  the  brain.  The  anterior  fibres  of  the  peduncles  enter 
the  corpora  striata,  and  the  posterior  fibres  join  the  optic  thai- 
ami,  before  continuing  into  the  cerebral  substance.  The  nerve 
fibres  which  enter  the  basal  ganglia  are  no  doubt  largely  con- 
nected with  nerve  cells  found  there. 

When  a  lesion  involves  both  the  corpus  striatum  and  optic 
thalamas  of  one  side,  there  is  loss  of  voluntary  motion  and  of 
sensation  on  the  opposite  side  of  the  body,  without  necessary 
impairment  of  intellectual  faculties. 

It  is  probable  that  the  basal  ganglia  act  as  sets  of  relay  sta- 
tions which  mediate  between  the  cerebral  cortex  and  nervous 
centres  in  lower  parts  of  the  brain  and  spinal  cord. 

There  is  some  reason  to  believe  that  the  corpora  striata  are 
chiefly  concerned  in  the  modification  of  volitional  impulses 
passing  to  it  from  the  cerebral  convolutions ;  and  that  the  optic 
thalami  receive  the  sensory  impulses  before  they  proceed  to 
the  surface  of  the  brain. 

Injury  to  the  optic  thalami  is  followed  by  blindness  or  im- 
perfection of  vision. 

THE  CORPORA  QUADRIGEM1NA. 

These  bodies  correspond  to  the  corpora  bigemina,  or  optic 
lobes,  of  the  frog  and  pigeon. 

The  nervous  centres  for  the  co-ordination  of  the  movement 
of  the  eyeballs  with  the  contraction  of  the  pupils  lie  in  or  be- 
low the  anterior  half  of  the  corpora  quadrigemina. 

The  manner  in  which  the  actions  of  these  centres  are  asso- 


—109— 

ciated  ;  when  the  visual  axes  are  converged  the  pupils  contract, 
when  the  axes  becomes  parallel  the  pupils  dilate. 

Movements  of  the  opposite  eye  are  brought  about  by  the 
stimulation  of  the  corpora  quadrigemina,  on  one  side.  The  eye 
as  an  organ  of  expression. 

The  "  fixation  reflex." 

Extirpation  of  the  corpora  quadrigemina,  or  of  the  optic 
lobes,  on  one  side  produces  blindness  in  the  opposite  eye.  The 
effects  of  pathological  leisons  involving  various  parts  of  the 
visual  apparatus. 

In  the  rabbit  the  decussation  in  the  optic  chiasma  is  com- 
plete; in  the  dog  it  is  incomplete,  and  in  man  probably  incom- 
plete.   Hemiopia. 

The  seat  of  visual  sensations  appears  to  be  in  the  corpora 
quadrigemina,  but  visual  perceptions  are  lost  when  the  cere- 
bral cortex  is  destroyed. 

The  gradual  elaboration  of  perfect  perceptions  through'the 
successive  activity  of  various  nerve  centres. 

Other  physiological  functions,  as  that  of  respiration,  prob- 
ably are  regulated  by  special  centres  situaited  in  the  corpora 
quadrigemina. 

THE  CEREBELLUM. 

The  structure  of  the  cerebellum  and  the  manner  of  its  as- 
sociation. 

The  chief  function  of  the  cerebellum  is  to  serve  as  a  col- 
lection of  nerve  centres  whose  action  maintains  the  equilib- 
rium of  the  body  and  co-ordinates  its  movements. 

Lesions  of  the  cerebellum  artificially  produced  are  followed 
by  unsteadiness  of  gait,  and  when  a  large  amount  of  nervous 
substance  is  lost  complete  failure  of  co-ordination  is  the  result. 

Lateral  lesions  produce  more  effect  than  those  established 
in  the  median  line. 

Extensive  asymmetrical  injury  of  the  cerebellum,  as  of 
section  of  the  middle  peduncle  on  one  side,  produces  remark- 
able forced  movements  of  the  animal,  together  with  a  peculiar 
rolling  back  and  forth  of  the  eyes. 

Section  of  one  of  the  crura  cerebri  is  also  followed  b}r  forced 


—  110  — 

movements,  as  also  are  injuries  of  the  corpora  striata  and  optic 
thalami,  or  even  of  the  cerebral  cortex  alone. 

The  passage  of  a  galvanic  current  through  the  back  part 
of  the  head  produces  a  sensation  of  giddiness  and  a  rolling 
motion  of  the  eyes. 

There  is  no  reason  to  believe  that  the  cerebellum  is  con- 
nected with  the  sexual  functions.  The  special  sexual  centres 
appear  to  be  situaited  in  the  lumbar  region  of  the  spinal  cord. 

The  cerebellum  is  probably  capable  of  learning  to  carry 
out  refiexly  new  and  complicated  purposive  actions. 

The  functions  of  the  infant's  brain.     The  suckling  reflex. 

General  consideration  of  the  relation  of  the  activities  of 
the  various  parts  of  the  central  nervous  system.  The  estab- 
lishment as  reflexes  of  often  repeated  volitional  actions. 

THE  SEMI-CIRCULAR  CANALS  AND  THEIR  RELA- 
TION TO  THE  MAINTENANCE  OF  THE  EQUILI- 
BRUM  OF  THE  BODY. 

THE  STRUCTURE  OP  THE  SEMI-CIRCULAR  CANALS. 

The  planes  of  the  three  membranous  canals  lie  approxi- 
mately in  the  three  dimensions  of  space. 

The  ampullar  enlargement  of  each  canal  and  the  modified 
termination  of  the  filaments  of  the  auditory  nerve  within  it. 

The  cavity  of  each  canal  communicates  with  that  of  the 
utricle. 

The  whole  membranous  labyrinth  is  filled  with  endolymph. 

THE  EFFECT  OF  CUTTING  THE  SEMI-CIRCULAR  CANALS 

IN  A  PIGEON. 

When  one  of  the  semi-circular  canals  of  a  pigeon  is  divid- 
ed, remarkable  disturbances  of  equilibrium  immediately  fol- 
low. When  one  of  the  horizontal  canals  is  cut,  the  head  moves 
from  side  to  side ;  when  one  of  the  vertical  canals  is  operated 
on,  the  movement  is  up  and  down.  These  disturbances  of 
equilibrium  become  more  marked  when  a  number  of  canals  is 
divided,  and  the  animal  places  its  head  in  unusual  positions 
with  respect  to  the  body.  Gradual  recovery  takes  place  if  but 
one  or  two  canals  be  injured. 


— Ill— 

Injury  of  the  semi -circular  canals  of  the  mammal  is  fol- 
lowed by  the  same  general  results  as  in  the  case  of  the  pigeon. 

These  results  are  not  due  to  partial  muscular  paralysis,  nor 
probably  to  unusual  auditory  sensations. 

THE  SENSE  OF  EQUILIBEUM. 

The  maintenance  of  the  equilibrium  of  the  body  requires 
the  co-ordinated  activity  of  complicated  nerve-muscular 
mechanisms.  The  afferent  impulses  which  determine  the 
action  of  this  motor  apparatus  may  arrive  from  different 
sources. 

The  body  must  know  its  position  in  reference  to  sur- 
rounding objects  in  order  to  maintain  its  equilibrium.  Such 
a  knowledge  of  the  body's  position  may  be  attained  through 
visual  sensations,  tactile  sensations,  and  muscular  sensations. 

But  it  has  been  shown  that  a  person  may  be  conscious  of  a 
change  of  position  without  the  excitement  of  any  of  the  fore- 
going sensations.  The  impulses  which  bring  this  information 
are  supposed  by  some  to  arise  in  the  semi-circular  canals.  It 
is  possible  that  movements  of  the  body  may  cause  a  change  of 
pressure  of  the  endolymph  within  the  semi-circular  canals  up- 
on the  nervous  mechanisms  there,  the  intensity  of  excitement 
in  each  impulla  depending  upon  the  direction  of  the  move- 
ment.    The  truth  of  this  hypothesis  is  not  established. 

The  various  means  by  which  vertigo  may  be  produced. 

THE  CRURA  CEREBRI  AND  PONS  VAROLII. 

These  bodies  contain  considerable  gray  matter,  but  the 
chief  functions  we  can  ascribe  to  them  are  those  in  which  they 
serve  as  connecting  links  between  different  parts  of  the  central 
nervous  system.  Marked  disturbance  of  equilibrium  follows 
injury  of  either  the  crura  cerebri  or  the  pons  varolii. 

THE  BLOOD  SUPPLY  OF  THE  BRAIN. 

The  amount  of  blood  supplied  in  the  brain  is,  in  proportion 
to  the  size  of  the  organ,  probably  small. 

When  the  brain  is  exposed  it  is  found  to  undergo  rhythmic 


—112— 

alterations  of  volume,  occasioned  by  the  heart-beats  and, re- 
spiratory movements. 

During  its  period  of  activity  the  brain  appears  to  receive 
more  blood  than  when  at  rest. 

Owing  to  the  rigid  cranial  envelope  sudden  variations  of 
the  amount  of  blood  in  tne  brain  subject  its  substance  to  such 
changes  of  pressure  as  may  affect  the  consciousness. 

Function  of  the  cerebro-spinal  fluid. 

The  blood  supply  of  the  brain  is  no  doubt  under  elaborate 
vaso-motor  regulation. 

General  conception  of  the  functions  of  the  nervous  system. 


XIX.   THE  EYE  AND  SIGHT. 

The  anatomical  mechanism  whose  excitement  gives  rise  to 
a  simple  sensation  consists  of  (1)  a  peripheral  ''  sense  organ," 
(2)  an  afferent  nerve,  (3)  a  central  nerve-cell  organ. 

It  is  only  the  activity  of  the  central  organ  which  directly 
affects  consciousness.  It  is  often  difficult  to  determine  in  which 
part  of  the  sense  apparatus  the  disturbance  which  gives  rise  to 
a  sensation  originates. 

The  difference  between  physical  and  physiological  vt  light." 
The  sensitiveness  of  the  retina  to  certain  ether  vibrations. 

Specific  nerve  energy. 

The  difference  between  simple  sensations  and  judgments. 

THE  STRUCTURE  OF  THE  EYE  AND  PARTS  NEAR  IT. 

The  small  third  eyelid  which  represents  the  nictitating 
membrane  of  some  animals. 

The  perforated  lachrymal  papillae.  The  lachrymal  gland. 
The  Meibomian  glands. 

The  action  of  the  accessory  glandular  and  muscular  me- 
chanisms of  the  eye. 

The  reflex  secretions  from  the  lachrymal  glands,  and  the 
aid  rendered  by  winking  movements  to  the  emptying  of  the 
lachrymal  canals. 

The  six  muscles  for  the  movement  of  the  eyeball. 

The  eyeball.  The  oblique  entrance  of  the  optic  nerve. 
The  sclerotic  coat  and  cornea  continuous  with  it.  The  radius  of 
curvature  of  the  cornea  is  smaller  than  that  of  the  remaining 
surface  of  the  eyeball.  The  choroid  coat ;  its  blood-vessels, 
pigment- cells,  and  ciliary  processes.  The  iris;  its  inner  circu- 
lar and  outer  radial  plain  muscle  fibres ;  its  vessels,  nerves  and 
pigment.  The  ciliary  muscles.  The  crystalline  lens  ;  its  sus- 
pensory ligament.  The  sheet  of  tissue  known  as  the  "  sus- 
pensory ligament "  is  attached  at  its  inner  edge  to  the  anterior 
surface  of  the  lens,  and  at  its  outer  edge  to  the  inner  surface  of 


—  114  — 

the  ciliary  processes.  The  vitreous  humour  and  hyaloid  mem- 
brane. The  aqueous  humour.  The  anterior  and  posterior 
chambers  of  the  aqueous  humour.  The  canal  of  Schlemm. 
The  retina;  the  or  a  serrata;  the  macula  lutea  and  fovea  cen- 
tralis; the  blood-vessels  of  the  optic  nerve  and  their  distribu- 
tion in  the  retina. 

Commencing  at  its  anterior  surface  there  may  be  recog- 
nized in  the  human  retina  ten  distinct  layers ;  (1)  Membrana 
limitans  interna  ;  (2)  layer  of  nerve  fibres  ;  (3)  layer  of  nerve 
cells;  (4)  inner  molecular  layer ;  (5)  inner  nuclear  layer;  (6) 
outer  molecular  layea  ;  (7)  outer  nuclear  layer;  (8)  membrana 
limitans  externa;  (9)  layer  of  rods  and  cones;  (10)  layer  of 
tessellated,  pigment-holding  cells. 

The  macula  lutea,  or  yellow  spot,  is  free  from  blood-vessels 
except  at  its  margin.  The  blood-vessels  of  the  retina  ramify 
in  the  nerve  fibre  layer,  and  their  capillaries  do  not  extend  out- 
ward beyond  the  inner  nuclear  layer. 

The  fovea  centralis  contains  only  the  retinal  cones,  the 
rods  being  there  absent. 

The  optical  advantages  accruing  to  the  fovea  centralis,  as 
the  spot  of  distinct  vision,  from  the  absence  of  blood-vessels 
and  of  the  inner  retinal  layers  in  it. 

Th9  pigment-free  part  of  the  choroid  which  forms  the  tape- 
turn  in  some  animals. 

THE  EYE  AS  AN  OPTICAL  INSTRUMENT. 

When  a  ray  of  light  falls  on  the  retina  we  become  con- 
scious of  a  sensation  of  light. 

In  order  that  we  may  become  aware  of  the  form  of  a  dis- 
tant object,  an  image  of  it  must  be  thrown  upon  the  retina. 

The  laws  determining  the  formation  of  images  in  an  ordin- 
ary camera.    The  camera  obscura. 

The  eye  is  a  camera  made  up  of  a  dark  chamber  to  which 
the  light  is  admitted  through  a  diaphragm,  the  iris ;  two  re- 
fracting media,  the  cornea  and  crystalline  lens,  intercept  the 
light  before  its  entrance  into  the  retinal  chamber. 

The  refracting  power  of  a  lens  depends  (a)  upon  the  cur- 
vature of  its  surface,  (b)  upon  the  refracting  power  of  its  sub- 
stance. 


—115 — 

The  foci  of  all  the  refracting  media  of  the  eye  fall  upon 
an  optic  axis  which  meets  the  retina  a  little  above  and  inside 
of  the  fovea  centralis. 

We  may  calculate  the  path  of  all  oblique  rays  entering  the 
eye  by  assuming  that  they  meet  the  optical  axis  at  a  "  nodal " 
point  and  leave  the  axis  in  a  direction  parallel  to  the  first  from 
a  second  nodal  point.  The  nodal  points  are  near  together 
on  the  optical  axis  within  the  lens.  Primary  and  secondary 
optical  axes. 

The  refraction  of  a  ray  of  light  entering  the  eye  occurs 
chiefly  at  the  anterior  surface  of  the  cornea  and  at  the  anterior 
and  posterior  surfaces  of  the  lens. 

The  inversion  of  the  retinal  image. 

The  spatial  projection  of  retinal  impressions. 

When  the  head  is  plunged  under  water  ~the  refraction  by 
the  cornea  is  nearly  done  away  with ;  hence  the  marked  com- 
pensatory curvature  of  the  fish's  lens. 

The  anterior  and  posterior  surfaces  of  the  cornea  being 
nearly  parallel,  they  may  be  regarded  as  one. 

The  refractive  powers  of  the  aqueous  and  vitreous  hum- 
ours being  nearly  the  same  as  that  of  the  cornea,  we  may  regard 
the  refracting  surfaces  of  the  lens  as  three,  the  anterior  sur- 
face of  the  cornea,  the  anterior  and  posterior  surfaces  of  the 
lens. 

It  is  calculated  that  the  focus  of  the  refracting  media  of 
the  eye  lies,  for  parallel  rays,  14.647  mm.  behind  the  posterior 
surface  of  the  lens  and  22.647  mm.  behind  the  anterior  surface 
of  the  cornea. 

The  reason  why  the  pupil  of  an  observed  eye  appears  dark. 
Albinos.    Principle  of  the  opthalmoscope. 

The  luminous  eyes  of  some  nocturnal  animals. 

ACCOMMODATION. 

The  focal  distance  at  which  a  distinct  image  of  an  object 
may  be  formed  by  light  passing  through  a  refracting  surface, 
the  refractive  index  remaining  the  same,  depends,  (a)  upon 
the  curvature  of  the  surface,  (b)  on  the  angle  which  the  enter- 
ing rays  form  with  it.  In  order  that  an  image  which  is  thrown 
i5 


—116— 

upon  a  certain  fixed  plane  may  remain  distinct  when  one  of 
those  factors  is  changed,  the  other  factor  must  undergo  a  com- 
pensatory change. 

.    If  this  accommodation  is  not  brought  about,  the  image  is 
replaced  by  a  series  of  blurred  "  diffusion  circles." 

Accommodation  in  the  human  eye  as  illustrated  by  "Schei- 
ner's  experiment."    The  near  limit  of  distinct  vision. 

In  the  normal  or  emmetropic  eye,  the  near  limit  is  at  a  dis- 
tance of  ten  to  twelve  centimetres;  the  far  limit  may  be  re- 
garded as  at  an  infinite  distance.  In  the  sort  sighted  or  myopic 
eye  the  near  limit  is  brought  within  five  to  six  centimetres 
distance  of  the  cornea  and  the  far  limit  at  a  variable  but  not 
considerable  distance.  In  the  far  sighted  or  hypermetropic 
eye,  the  near  limit  of  distinct  vision  is  some  distance  away, 
and  a  far  limit  does  not  exist.  In  the  three  cases,  an  image 
formed  by  rays  parallel  to  the  optical  axis  falls  respectively  on 
the  retina;  before  it  and  behind  it.  The  presbyopic  eyes  of  old 
people. 

The  structural  or  physiological  peculiarities  which  occasion 
these  various  defects. 

THE  APPARATUS  OF  ACCOMMODATION. 

While  at  rest  the  eye  is  accommodated  for  objects  at  an 
extreme  distance. 

In  accommodation  for  near  objects  two  movements  may  be 
observed  in  the  eye,  (1)  a  narrowing  of  the  pupil,  (2)  a  change 
in  the  curvature  of  the  anterior  surface  of  the  lens  by  which  it 
becomes  more  convex. 

In  its  normal  condition  the  lens  is  an  elastic  body  whose 
curved  surfaces  are  somewhat  flattened  by  the  pressure  of  the 
inclosing  suspensory  ligament  which  is  kept  stretched  by  its 
attachment  to  the  choroid.  When  the  ciliary  muscles  contract, 
the  choroid  is  pulled  forward  and  the  suspensory  ligament  is 
slackened,  thus  allowing  the  anterior  surface  of  the  lens  to 
bulge  outward. 

Proof  that  accommodation  is  accomplished  by  change  in  cur- 
vature of  the  anterior  surface  of  the  lens. 

THE  MOVEMENTS  OF  THE  PUPIL. 

The  pupil  is  contracted  when  light  falls  upon  the  retina, 


—117— 

but  is  dilated  in  the  dark.  It  is  contracted  when  we  accommo- 
date for  near  objects,  but  it  is  dilated  when  we  accommodate  for 
distant  ones.  It  is  contracted  when  the  optical  axes  converge 
and  dilated  when  they  become  parallel. 

The  contraction  of  the  pupil  is  an  active  movement;  it  is 
not  certain  whether  dilation  of  the  pupil  is  due  to  the  contrac- 
tion of  radial  muscle  fibres  or  to  simple  inhibition  of  the  activ- 
ity of  the  circular  muscles. 

The  condition  of  the  eye  during  sleep. 

These  movements  of  the  pupil  are  the  result  of  reflex  and 
associated  actions.  When  the  movement  is  brought  about  by 
light  falling  upon  the  retina,  the  optic  nerve  is  the  afferent 
nerve  of  the  reflex  apparatus  ;  the  third  or  oculo-motor  nerve 
is  the  efferent  nerve  whose  excitement  causes  contraction,  and 
the  sympathetic  is  the  efferent  dilator  nerve. 

There  is  union  between  the  reflex  centres  for  movement  of 
the  pupils;  for  subjecting  one  eye  to  changes  of  illumination 
produces  movement  of  the  opposite  pupil. 

The  action  of  drugs  upon  the  pupil,  as  of  atropin  or  physo- 
stigmin,  is  probably  wholly  local. 

ADVANTAGES  AND  DEFECTS   OF    THE  EYE  AS  AN   OPTI- 
CAL APPARATUS.     • 

Owing  to  the  accommodating  power,  the  place  of  formation 
of  all  images  in  the  eye  is  at  the  principal  focus. 

The  theoretically  perfect  defining  power  of  the  eye  in  the 
region  of  the  fovea  centralis. 

When  light  passes  through  a  spherical  lens  it  can  throw  a 
well-defined  image  of  larger  dimensions  upon  a  curved  surface, 
like  that  of  the  retina,  than  upon  a  plane  surface. 

The  special  defects  of  the  myopic,  hypermetropic  and  pres- 
byopic eye. 

The  spherical  aberration  due  to  the  form  of  the  lens  is 
probably  insignificant  in  comparison  with  other  optical  defects 
of  the  eye.  The  refractive  power  of  the  lens  varies  in  different 
parts  of  it.  The  most  obvious  use  of  the  iris  is  to  diminish 
spherical  aberration  by  cutting  off  circumferential  rays. 

The  refracting  surfaces  of  the  eye  are  not  perfect  sections 
of  a  sphere,  but  are  often  more  convex  along  one  meridian  than 


—118— 

another.  Hence,  lines  having  different  directions  cannot  all  be 
brought  simultaneously  to  a  focus  on  the  retina.  This  leads  to 
the  defect  known  as  astigmatism.   Illustrations  of  astigmatism. 

Methods  of  determining  the  chromatic  aberration  of  the 
eye. 

Entopic  Phenomena. — Floating  particles  in  the  vitreous 
humour,  the  musccB  volitantes.  Imperfections  in  the  lens. 
Tears  on  the  cornea.  The  observation  of  the  margin  of  the 
pupil.  The  luminosity  and  the  floating  colored  clouds  of  the 
retina. 

The  refracting  surfaces  of  the  eye  are  not  centred  on  the 
optic  axis. 

SENSATIONS  OF  VISION. 

The  education  of  the  senses. 

The  part  of  the  retina  which  is  directly  excited  by  light  is 
the  posterior  layer  of  rods  and  cones. 

The  optic  nerve  itself  is  unirritable  towards  light.  The 
Mind  spot.  The  shadows  of  the  retinal  blood-vessels  seen  as 
PurMnje's  figures. 

The  amount  of  energy  contained  in  a  luminous  wave  may 
be  exceedingly  small. 

The  movement  of  pigment  in  the  retinal  epithelium  under 
the  influence  of  light. 

The  reflex  movements  of  the  cones  under  the  influence  of 
light, 

The  retinal  pigments  which  are  altered  by  light. 

Both  rods  and  cones  are  probably  directly  irritated  by 
light ;  in  certain  animals  the  first  and  in  others  the  second  of 
these  elements  seems  to  be  absent.  It  has  been  conjectured 
that  rods  serve  chiefly  to  give  mere  sensation  of  light,  while 
the  cones  are  adapted  to  permit  of  distinctness  of  vision. 

The  demonstration  of  the  yellow  pigment  of  the  macula 
lutea. 

Perception  of  the  rods  and  cones  of  one's  own  retina. 

The  alternate  spontaneous  blindness  of  the  two  eyes. 

Temporary  blindness  produced  by  pressure  on  the  bulb. 

THE  RELATION  OF  THE   DURATION  AND   STRENGTH   OF 
THE  STIMULUS  TO  THE  SENSATION. 

Subjective  and  objective  light. 


—119— 

The  sensation  produced  by  a  momentary  flash  of  light  has 
a  much  longer  duration  than  the  stimulus  itself;  when  single 
flashes  follow  each  other  sufficiently  rapidly  the  separate  sensa- 
tions are  fused.  The  intervals  between  the  flashes  must  be 
smaller  the  stronger^  the  light,  in  order  that  the  separate  sen- 
sations may  be  completely  fused.  The  duration  of  the  "  after 
image  "  is  longer  the  stronger  the  light  which  caused  the  sensa- 
tion. 

"  Positive  "  and  "  negative  "  after-images. 

Instantaneous  photography.  Apparent  motion  produced 
by  the  fusion  of  sensations  from  momentary  stimuli. 

The  intensity  of  sensation  varies  with  the  intensity  of  illu- 
mination ;  but  the  relation  of  the  variation  of  the  intensities  is 
not  a  simple  one. 

Weber's  Law. — The  increase  of  stimulus  which  is  neces- 
sary to  produce  the  smallest  increase  of  sensation  bears  always 
the  same  proportion  to  the  whole  intensity  of  the  stimulus 
which  has  already  been  applied.  Practical  application  of  this 
law. 

THE  DISTINCTION  AND  FUSION  OF  SIMULTANEOUS  SEN- 
SATIONS. 

Two  objects  appear  as  one  if  brought  near  enough  together. 
In  order  to  appear  as  two  objects,  the  distance  between  their 
images  on  the  retina  must  be  not  less  than  the  diameter  of  a 
single  retinal  cone.  In  the  human  eye  objects  thrown  thus  near 
together  in  the  fovea  of  the  retina  may  still  be  distinguished 
apart.  Toward  the  periphery  of  the  retina  the  distinction  is 
not  nearly  so  fine.  Green  and  blue  light,  in  the  order  named, 
each  permit  of  finer  definition  than  white  light,  while  red  light 
is  least  advantageous. 

Cause  of  the  broken  outline  of  fine,  parallel  lines,  which 
are  drawn  close  together. 

The  distinction  between  cerebral  and  retinal  visual  areas. 

The  number  of  cones  in  the  retina  is  much  greater  than 
that  of  the  fibres  in  the  optic  nerve. 

COLOR  SENSATIOJNS. 
Besides  the  sensations  of  whi  e  and    fo  a'k,  we  may  attain 


—120— 

certain  sensations  of  color,  the  quality  of  each  of  which  is  de- 
termined by  the  wave  length  of  the  incident  light.  The  spec- 
tral colors  are  red,  orange,  yellow,  green,  blue,  violet.  The 
fusion  of  blue  and  red  produces  another  simple  color, purple, 
not  found  in  the  spectrum.     The  physical  cause  of  color. 

All  the  hues  of  nature  may  be  imitated  by  the  proper 
fusion  of  the  primary  color  sensations  with  each  other  or  with 
white  or  black. 

The  origin  of  browns,  and  olive  greens.  Various  methods 
and  the  results  of  mixing  simple  color  sensations. 

The  cause  of  the  difference  between  the' sensation  obtained 
by  the  mixture  of  two  colors  on  the  retina  and  that  derived 
from  the  mixture  of  the  pigments  themselves. 

A  color  is  said  to  be  more  or  less  saturated  according  as  it. 
contains  less  or  more  of  white  light.  No  color  is  absolutely 
saturated. 

Every  color  which  is  sufficiently  illuminated  appears  white. 

Stimulation  of  a  considerable  retinal  area  is  necessar}T  to 
excite  a  sensation  of  color;  very  small  colored  objects  appear 
black. 

Color  sensation  produced  by  electric  stimulation  of  the  eye. 

Gray  is  a  mixture  of  white  and  black. 

Complementary  colors  are  those  which,  when  mixed  on  the 
retina,  produce  the  sensation  of  white  light. 

The  following  are  complementary  colors  : — Red  and  green- 
blue;  orange  and  cyan-blue;  yellow  and  ultramarine  blue ; 
greenish-yellow  and  violet ;  green  and  purple. 

Any  three  colors,  situated  in  the  spectrum  as  far  apart  as 
possible,  may,  in  proper  proportions,  together  produce  white ; 
by  varying  the  proportions,  all  of  the  other  spectral  colors  may 
be  derived  from  the  three  primary  colors. 

The  Heriny  theory  of  color  sensation. 

The  Young  Helmholtz  theory  of  color  sensation. 

The  difference  of  sensitiveness  of  the  retina  to  different 
colors.  In  a  waning  light  the  red  sensations  disappear  first  and 
the  blue  last ;  hence  red  objects  first  become  dark. 

COLOEED  AFTER-IMAGES. 

The  sensation  of  light  lasting  longer  than  the  stimulus,  an 


— 121  — 

object  may  still  be  seen  for  a  time  after  its  removal  from  the 
fieJd  of  vision;  such  sensations  are  known  as  after  images. 
The  after-image  is  at  first  positive,  or  of  the  same  brightness 
and  color  as  the  stimulus ;  soon  it  becomes  negative,  or  of 
brightness  and  color  complementary  to  the  original  stimulus. 

Successive  Contrast.  The  greater  saturation  of  a  color  by 
contrast.  Colors  whose  influence  is  mutually  aiding  or  deteri- 
orating. 

The  conditions  of  the  retina  upon  which  depend  the  bright- 
ness or  darkness  of  an  after-image. 

Explanation  of  changes  in  after-images  as  a  result  of  re- 
tinal fatigue. 

The  successive  fadings  of  the  colors  of  an  after-image. 

The  intrinsic  light  of  the  retina. 

SIMULTANEOUS  CONTRAST. 

Light  and  dark  surfaces  appear  respectively  brighter  and 
darker  when  viewed  together.  The  phenomena  of  colored 
shadows.  When  a  piece  of  gray  paper  is  laid  on  a  colored 
ground  and  covered  with  tissue  paper,  the  gray  slip  appears  to 
have  a  color  complementary  to  that  of  the  surface.  The  com- 
parison of  strips  of  black  paper  respectively  seen  through  and 
reflected  by  colored  glass  plates. 

The  physiological  influence  of  light  which  penetrates  the 
sclerotic  coat. 

The  phenomena  of  simultaneous  contrast  occur  as  if  every 
colored  image  which  falls  upon  the  retina  rendered  the  neigh- 
boring parts  of  the  retina  more  irritable  toward  the  comple- 
mentary color. 

The  physiological  basis  of  taste  in  color. 

COLOR  BLINDNESS. 

Some  persons  are  incapable  of  acquiring  certain  color  sen- 
sations. The  most  common  form  of  the  defect  is  that  of  "  red- 
blindness."  To  persons  suffering  from  it,  the  colors  rose-red 
and  bluish-green  are  identical.  They  distinguish  in  the  spec- 
trum but  two  colors,  calling  them  yellow  and  blue  ;  under  the 
yellow  they  include  the  red,  orange,  yellow  and  green,  and 
b  ue  and  violet  are  called  blue. 


—122— 

About  5  p.  c.  of  the  population  are  affected  to  some  degree 
with  red-blindness. 

Temporary  color-blindness  induced  by  wearing  colored 
glasses,  and  by  the  ingestion  of  santonin. 

A  rarer  form  of  color-blindness  is  said  to  occur  in  which  the 
sensation  of  red  is  preserved  but  that  of  green  is  lost. 

Color-blindness  on  the  periphery  of  the  retina. 

Methods  of  testing  for  color-blindness. 

VISUAL  PERCEPTIONS. 

The  mind  derives  ideas  from  simple  visual  sensations ;  sen- 
sations give  rise  to  visual  perceptions. 

In  most  of  our  visual  ideas  we  take  little  account  of  simple 
sensations,  but  use  directly  the  complex  judgments  founded  on 
them. 

The  psychical  effects  produced  by  viewing  a  landscape 
through  differently  colored  glasses. 

The  perception  of  the  positions  of  objects.  The  localiza- 
tion of  objects  by  vision  is  a  subjective  process.  The  images  of 
objects  are  inverted  on  the  retina. 

MODIFIED  PERCEPTIONS. 

Irradiation  :  bright  objects  appear  larger  than  dark  ones  of 
the  same  size.    Illustrations. 

The  blind  spot  is  not  perceived  chiefly  because  no  sensation 
is  aroused  by  it. 

The  retina  itself  gives  rise  in  the  dark  to  luminous  sensa- 
sions. 

Intrinsic  colored  images  of  the  retina.  Lights  produced  by 
pressure  on  the  eyeball.  Effect  of  stimulating  the  eye  or  optic 
nerve. 

Visual  judgments  of  size.  The  only  method  of  determin- 
ing the  relative  size  of  objects  is  the  comparison  of  the  magni- 
tude of  their  images  thrown  upon  the  retina ;  our  estimation 
of  their  real  size  depends  upon  the  distance  from  the  eye  at 
which  they  are  believed  to  be  situated.  This  distance  seems 
greater  when  subdivided  by  intervening  objects  and  when  seen 
obscurely ;  the  apparent  size  of  the  moon  in  mid-sky  and  on 
the  horizon  ;  comparison  of  the  lengths  of  two  equal  lines,  one 


—123— 

of  which  is  subdivided  and  the  other  not ;  the  greater  apparent 
size  of  objects  in  a  fog.  The  appreciation  of  difference  of  size 
by  contrast. 

Judgments  of  the  magnitude  of  angles. 

VISION  WITH  TWO  EYES. 

In  general,  the  reason  why  an  object  viewed  with  two  eyes 
appears  single  is  that  the  image  of  each  point  on  it  falls  upon 
''corresponding"  or  "identical"  areas  of  the  two  retinas. 
Points  on  the  inner  side  of  one  retina  have  their  corresponding 
points  on  homologous  parts  of  the  outer  side  of  the  other. 

MOVEMENTS  OF  THE  EYEBALLS. 

The  orbit  and  the  eyeball  form  a  ball  and  socket  joint,  the 
centre  of  rotation  being  1.8  mm.  behind  the  centre  of  the  eye. 

The  reflex  fixation  of  external  objects  which  keeps  the  eye- 
ball at  rest  when  the  head  is  moved. 

The  "primary"  and  "secondary"  positions  of  the  eye. 
The  position  of  the  resting  eye. 

The  rotation  of  the  eye  around  its  visual  axis  when  the 
latter  is  changed  from  a  primary  to  an  oblique  position. 

The  muscles  of  the  eyeball  and  the  movements  brought 
about  by  their  action. 

The  co-ordination  of  the  movements  of  the  eyeball.  The 
double  images  that  result  when  the  co-ordination  centre  fails  to 
act. 

Apparent  rotation  of  toothed  wheels  brought  about  by  the 
rinsing  motion. 

False  judgments  of  motion. 

THE  HOROPTER. 

Distinct  vision  of  objects  can  be  had  only  when  the  images 
of  their  parts  fall  upon  corresponding  points  of  the  two  retinas. 
In  any  given  position  of  the  visual  axes  such  corresponding- 
points  are  projected  outward  upon  some  definite  line  or  surface, 
and  this  line  or  area  of  distinct  vision  is  known  as  the  horopter. 
The  horopter  changes  its  form  or  position  with  changes  of  di- 
rection of  the  visual  axes.     When  standing  erect  and  looking 

toward  the  horizon  the  horopter  is  upon  the  ground  before  the 
16 


—124— 

eyes.    The  precautions  necessary  in  walking  upon  a  hillside,  or 
upon  a  level  while  looking  through  a  prism. 

Model  demonstrating  the  change  in  form  and  position  of 
the  horopter  with  alteration  of  the  visual  angle. 

THE   JUDGMENTS   THAT   AKISE    FROM    BINOCULAR 

VISION. 

By  means  of  the  movements  of  the  two  eyeballs  and  the 
images  falling  upon  corresponding  point  of  the  two  retinas,  we 
are  enabled  to  form  certain  judgments  concerning  the  form, 
size,  and  distance  of  objects. 

Illustrations  of  the  judgments  concerning  size  and  distance 
as  depending  on  the  "'  muscular  sense  "  of  innervation  of  the 
eye-muscles. 

The  idea  of  perspective  aroused  by  the  shading  and  color- 
ing of  objects. 

When  a  solid  object  is  viewed,  the  images  falling  upon  the 
two  retinas  cannot  be  identical ;  they,  however,  do  not  give  rise 
to  double  vision,  but  are  fused  in  the  cerebrum  so  as  to  give 
the  perception  of  single  solid  objects.  The  shading  of  an  ob- 
ject largely  assists  in  the  formation  of  a  judgment  of  its 
solidity. 

Applications  of  the  stereoscope.    The  telestereoscope. 

Visual  combinations  of  objects  without  the  stereoscope. 
Combination  with  crossed  or  parallel  visual  axes. 

Stereoscopic  effects  with  one  eye. 

The  psychical  influence  of  the  use  of  two  eyes. 

When  two  different  colors,  or  white  and  black,  are  viewed  at 
the  same  time,  each  by  one  eye,  there  is  not  a  fusion  of  color 
in  the  sensation  but  an  alternate  mastery  of  one  and  the  other. 


XI   THE  EAR  AND  HEARING. 

THE  STRUCTURE  OF  THE  EAR. 

The  organ  of  hearing  may  be  considered  to  be  made  up  of 
three  parts  ;  an  external  ear,  composed  of  the  pinna  and  audi- 
tory meatus,  the  latter  being  separated  by  the  tympanic  mem- 
brane from  the  middle  ear,  or  tympanum.  The  tympanum 
contains  the  auditory  ossicles,  malleus,  incus  and  stapes,  and 
its  cavity  opens  upon  the  upper  wall  of  the  pharynx  by  means 
of  the  Eustachian  tube ;  an  internal  ear,  consisting  of  a  mem- 
branous labyrinth,  to  which  the  auditory  nerve  is  distributed, 
which  is  contained  within  a  bony  labyrinth ;  the  two  laby- 
rinths are  filled  with  fluid  known  respectively  as  the  endolymph 
and  the  perilymph.  The  division  of  the  bony  labyrinth  into 
vestibule,  semi-circular  canals  and  cochlea.  The  fenestra 
rotunda  and  fenestra  ovalis  are  placed  in  the  bony  wall  sepa- 
rating the  tympanum  respectively  from  the  scala  tympani  of 
the  cochlea,  and  from  the  vestibule.  The  membranous  vesti- 
bule is  composed  of  two  sacs,  the  saccule  and  utricle,  whose 
cavities  are  indirectly  united.  The  membranous  semi-circular 
canals  spring  from  the  utricle,  and  the  cavity  of  the  saccule  is 
continuous  with  that  of  the  membranous  canal  of  the  cochlea. 
The  auditory  hair-cells  upon  the  maculae  of  the  vestibular  sacs 
and  on  the  cristas  of  the  ampullae  of  the  semi-circular  canals. 
The  otoliths  within  the  sacs  and  ampullae. 

The  microscopic  structure  of  the  membranous  cochlea  and 
of  the  organ  of  Oorti  contained  in  it. 

THE   SPECIAL  FUNCTIONS  OF  THE   PARTS   OF   THE 
ACOUSTIC  APPARATUS. 

THE  PINNA  OR  EXTERNAL  EAR. 

The  modification  of  the  concha  in  different  animals.  Its 
purpose  is  to  collect  the  waves  of  sound  from  the  external  air. 


—126— 

The  use  of  the  pinna  by  animals  in  determining  the  direc- 
tion of  sound. 

Incomplete  power  of  localizing  a  sounding  body  by  the 
sense  of  hearing. 

THE  MEMBEANA  TYMPANI. 

The  curved  surface  and  funnel -shape  of  the  tympanic 
membrane.  This  membrane  is  easily  set  vibrating  by  air 
waves,  and  has  no  fundamental  note  of  its  own.  Its  peculiar 
shape  adapts  it  for  transmitting  motions  of  great  amplitude 
and  small  energy  as  motions  of  small  amplitude  and  great 
energy. 

The  movements  of  the  auditory  ossicles.  The  ossicles 
form  a  sort  of  compound  lever  by  which  the  oscillations  of 
the  tympanic  membrane  are  exactly  transferred  to  the  mem- 
brane of  the  fenestra  ovalis,  but  with  diminished  amplitude 
and  correspondingly  increased  force. 

The  mean  extent  of  the  excursions  of  the  tip  of  the  malleus 
is  probably  near  1-28  mm.  The  excursions  of  the  stapes  are 
only  f  as  great,  but  are  1^  times  as  energetic. 

The  tensor  tympani  muscle  serves  by  its  contraction  to  pre- 
vent the  tympanic  membrane  being  pushed  out  too  far. 

The  laxator  tympani  muscle  probably  by  its  contraction 
causes  the  ear-drum  to  move  outward. 

The  stapedius  muscle  probably  acts  to  prevent  the  stapes 
being  driven  too  far  into  the  fenestra  ovalis. 

THE  EUSTACHIAN  TUBE. 

This  channel  connecting  the  middle  ear  and  the  pharynx 
serves  to  keep  the  pressure  within  the  tympanic  cavity  equal 
to  that  of  the  atmosphere.  The  tube  is  probably  only  opened 
during  the  act  of  swallowing. 

THE  GENERATION  OF  AUDITORY  SENSATIONS. 
THE  MEMBRANOUS  LABYRINTH. 

The  filaments  of  the  auditory  nerve  end  in  the  maculae  and 
cristas  of  the  internal  ear  and  in  the  basilar  membrane  of  the 
cochlea.    It  is  supposed  that  vibrations  of  the  endolymph  set 


—127 — 

these  end-organs  in  corresponding  motion,  thus  mechanically 
stimulating  the  auditory  nerve. 

The  distinction  between  physical  and  physiological  sound. 
Graphic  representation  of  air  waves. 

The  transmission  of  sound  through  the  bones  of  the  skull ; 
hearing  without  a  tympanic  membrane. 

Sounds  may  be  divided  into  musical  tones  which  are  caused 
by  rhythmic  or  periodic  vibrations  of  the  air,  and  noises  which 
are  due  to  non-periodic  vibrations. 

Sounds  are  distinguished  by  the  three  characters  of  loud- 
ness, pitch  and  quality.  The  physical  peculiarities  implied  in 
these  terms. 

The  physical  range  of  audible  tones. 

Each  musical  note  is  made  up  of  a  fundamentel  tone, 
which  determines  the  pitch,  with  which  a  greater  or  less  num- 
ber of  overtones  are  combined,  the  latter  determining  the 
quality  of  the  note. 

Overtones  have  2,  3,  4,  etc.,  times  the  rate  of  vibration  of 
the  fundamental.  Thus  for  the  fundamental  c  the  overtones 
are  c/  g/  c,"  e,"  g,"  etc. 

The  manner  in  which  the  partial  tones  are  produced  to- 
gether with  the  fundamental  tone.     It  is  the  varied  predomi 
nance  of  different  partials  which  causes  the  difference  of  qual- 
ity in  the  notes  of  various  musical  instruments. 

The  composite  air- waves  formed  by  the  fusion  of  partial 
vibrations. 

Neaiiv  every  body  capable  of  periodic  vibration  has  a  fun- 
damental tone  of  its  own.  The  tympanic  membrane  has  no 
particular  fundamental  tone. 

The  simple  arithmetical  relations  of  the  vibration  rates  of 
the  tones  of  a  musical  chord. 

The  production  of  musical  tones  and  notes  upon  the  siren. 

Sympathetic  vibrations.  The  analysis  and  synthesis  of 
musical  tones. 

The  high  fundamental  tone  of  the  external  auditory  meatus. 

There  is  reason  to  think  that  the  organ  of  Corti  may  be 
regarded  as  a  musical  instrument  capable  of  responding  by 
sympathetic  vibration  to  all  audible  tones. 

The  physiological  basis  of  the  musical  sense. 


—128— 

It  has  been  supposed  that  the  auditory  hairs  upon,  and  the 
otoliths  near,  the  maculas  and  cristae  of  the  labyrinth  are  con- 
cerned in  the  reproduction  of  irregular  vibrations  known  as 
noises. 

The  simplest  aural  apparatus  known  is  a  mere  sac  whose 
walls  are  set  with  hair-cells,  and  whose  cavity  is  filled  with 
fluid  containing  otoliths. 

When  single  sounds  are  repeated  with  sufficient  rapidity, 
they  fuse  into  a  continuous  tone  whose  pitch  is  determined  by 
the  rate  at  which  the  single  sounds  succeed  each  other. 

Vibrations  recurring  less  than  30  times  a  second  are  not 
heard  as  continuous  tones.  The  upper  limit  of  auditory  sensation 
is  reached  when  vibrations  recur  about  38,000  times  per  second. 
The  variation  of  this  limit  with  the  loudness  of  sound  and  with 
the  individual. 

The  power  of  distinguishing  pitch  differs  much  in  different 
parts  of  the  scale.  The  fineness  of  musical  appreciation  of 
quality  and  pitch. 

The  subjective  nature  of  sound.  Individual  differences  in 
the  appreciation  of  tones. 

AUDITORY  JUDGMENTS. 

Any  stimulation  of  the  auditory  nervous  apparatus  is  in- 
terpreted as  due  to  sound  waves. 

From  the  loudness,  quality,  and  pitch  of  sounds,  we  form 
judgment  as  to  their  origin,  direction  and  distance.  The  nature 
of  ventriloquism. 


XXI.   THE  ORGAN  AND  SENSE  OF  SMELL. 

The  cavity  of  the  nose  on  each  side  of  the  nasal  septum  is 
divided  functionally  into  a  lower  respiratory  and  upper  olfac- 
tory chamber.  The  olfactory  mucous  membrane,  to  which  the 
olfactory  nerve  is  distributed,  lines  the  upper  and.  middle  turbi- 
nated parts  of  the  fossas  and  the  upper  part  of  the  septum. 
The  ciliated  epithelium  and  mucous  glands  of  the  respiratory 
chambers  of  the  nose. 

The  termination  of  the  nerve  fibres  in  the  olfactory  cells  of 
the  upper  chamber. 

THE  ORIGIN  OF  SENSATIONS  OF  SMELL. 

Odorous  particles  are  carried  by  diffusion  into  the  olfactory 
chamber  of  the  nose,  or  drawn  into  it  by  active  inhalation. 

Odorous  bodies  must  come  into  contact  with  the  olfactory 
mucous  membrane  in  order  to  produce  a  sensation.  Filling 
the  nose  with  an  odorous  liquid  causes  no  sensation  of  smell, 
unless  the  fluid  be  one  which  readily  diffuses  into  the  mucous 
membrane.  When  several  odors  are  simultaneously  inhaled, 
the  peculiarity  of  each  may  be  distinguished. 

Localization  of  an  odor  by  the  sense  of  smell  is  very  im- 
perfect. 

The  sensation  requires  some  time  to  develope  itself  after 
application  of  the  stimulus,  and  may  last  for  a  considerable 
time. 

Certain  pungent  substances,  as  ammonia,  give  rise  to  sen- 
sations through  the  nose  which  are  not  those  of  smell  proper ; 
are  probably  due  to  stimulation  of  the  fifth  nerve.  There  may 
be  sensations  of  smell  of  purely  subjective  origin. 


XXII.   THE  OMAN  AND  SENSE  OF  TASTE. 

The  glossopharyngeal  and  the  lingual  nerves  are  the  special 
nerves  of  taste. 

The  modified  termination  of  the  gustatory  nerves  in  the 
mucous  membrane  of  the  tongue  and  palate. 

Many  sensations  which  we  are  accustomed  to  distinguish  as 
those  of  taste  are  really  sensations  of  smell. 

Sapid  substances  may  be  classified  as  sweet,  sour,  saline 
and  bitter.    They  act  in  solution  as  chemical  stimuli. 

Specific  energy  of  the  nerves  of  taste :  a  certain  substance 
gives  a  bitter  sensation  when  applied  to  one  part  of  the  tongue 
and  a  sweet  taste  when  laid  on  another  part. 

Sensations  of  taste  may  arise  from  mechanical  or  elec- 
trical stimulation  of  the  gustatory  apparatus. 


XXIII.   GENERAL  SENSIBILITY  AND  SENSATIONS  OF  TOUCH. 

The  distribution  and  modified  terminations  of  sensory 
nerves. 

We  possess  a  certain  faculty  of  general  sensibility  which 
gives  rise  to  a  consciousness  of  irritation  in  the  body  without 
enabling  us  to  localize  the  stimulus  or  distinguish  its  nature. 
Such  are  the  sensations  due  to  irritation  of  a  nerve  trunk  or 
of  the  viscera.  Such  sensations  readily  merge  into  those  of 
pain. 

The  more  special  sensations  of  feeling  are  those  derived 
from  touch,  temperature  and  muscular  activity. 

TACTILE  SENSATIONS. 
SENSATIONS  OF  PRESSURE. 

The  smallest  difference  which  can  be  distinguished  between 
two  unequal  weights  laid  upon  the  skin  is  proportional  to  the 
magnitude  of  the  weights. 

When  separate  sensations  of  contact  succeed  each  other 
with  sufficient  rapidity  they  become  fused. 

Not  all  parts  of  the  skin  are  equally  sensible  to  variations 
or  pressure. 

Sensations  of  contact  are  present  when  the  intensity  of 
the  pressure  is  varied,  and  fade  away  when  it  becomes  con- 
stant. 

A  cold  body  is  judged  to  be  heavier  than  a  warm  one  of 
equal  weight. 

There  is  reason  to  believe  that  there  exist  tactual  nerves 
distinct  from  those  of  general  sensibility. 

The  pressure  points  of  the  skin. 

TACTILE  PERCEPTIONS  AND  JUDGMENTS. 

Sensations  of   contact  are   referred  generally  to  definite 
localities  on  the  skin.     The  erroneous  judgments  that  arise 
17 


—132— 

from  the  irritation  of  the  nerves  of  an  amputated  limb.  Mis- 
taken judgments  arise  when  a  marble  is  rolled  between  the 
tips  of  two  crossed  fingers. 

The  power  localizing  contact  upon  the  skin  is  not  the  same 
in  all  parts.    The  division  of  the  skin  into  tactual  areas. 

The  power  of  localization  is  most  marked  upon  the  tip  of 
the  tongue  and  the  palmar  surface  of  the  finger,  and  least 
marked  upon  the  forearm,  sternum,  and  back. 

The  fineness  of  tactile  perception  in  greatly  increased  by 
exercise. 

The  judgments  concerning  the  hardness,  smoothness,  etc., 
of  bodies. 

THE  TEMPERATURE  SENSE. 

Bodies  warmer  or  colder  than  the  skin  when  in  contact 
with  it  gives  rise  to  sensations  gf  heat  or  cold.  The  erroneous 
judgments  that  may  arise  from  artificially  rendering  the  two 
hands  of  different  temperatures. 

The  range  of  finest  distinction  of  temperature  is  included 
between  limits  which  lie  near  the  body  temperature. 

Not  all  parts  are  equally  sensitive  to  variations  of  tempera- 
ture. 

There  are  probably  special  afferent  temperature  nerves 
which  are  irritated  by  variations  of  temperature.  The  warm 
and  cold  points  of  the  skin. 

There  is  reason  to  believe  that  the  sensations  of  heat,  cold, 
and  pressure,  respectively,  are  aroused  through  the  excitement 
of  different  sensory  nerves. 

THE  MUSCULAR  SENSE. 

We  commonly  estimate  the  weight  of  bodies  by  observing 
the  intensity  of  muscular  exertion  necessary  to  lift  them. 

Muscular  sensations  are  probably  peripheral  in  origin. 

The  effects  following  diminution  of  tactile  and  muscular 
sensibility  in  locomotor  ataxy. 

Judgements  wnich  arise  from  the  muscular  sense. 


XXIV.   PHYSIOLOGY  OF  THE  VOICE. 

STRUCTURE  OF    THE   LARYNX   AND   ACCESSORY  PARTS. 

The  air  chambers  above  and  below  the  larynx.  The  changes 
in  size  and  shape  of  which  they  are  capable. 

The  cartilages  of  the  larynx ; — the  thyroid,  cricoid  and  ary- 
tenoids ;  cartilages  of  Santorini  and  of  Wrisberg.  The  epi- 
glottis. 

The  ligaments ;  crico-thyroid  ;  thyro-hyoid. 

The  false  vocal  cords  ;  the  true  vocal  cords.  The  ventricles 
of  Morgagni.    The  mucous  membrane  of  the  larynx. 

The  glottis  : — glottis  vocalis  ;  glottis  respiratoria. 

The  intrinsic  muscles  of  the  larynx : — Posterior  crico- 
arytenoids ;  the  arytenoids,  transverse  and  oblique  ;  the  crico- 
thyroids ;  the  lateral  crico-arytenoids ;  the  aryteno-epiglot- 
tidean  ;  the  thyro-arytenoid.  All  are  in  pairs  except  the  ary- 
tenoids. 

The  nerves  of  the  larynx; — the  superior  and  inferior 
laryngeal  nerves. 

The  hyoidean  apparatus  ;  the  suspension  of  the  larynx 
and  its  extrinsic  muscles. 

ACTION  OF  THE  LARYNGEAL  MUSCLES. 

By  the  action  of  the  intrinsic  muscles  of  the  larynx  the 
vocal  cords  may  be  separated  or  approximated,  relaxed  or 
made  tense. 

In  quiet  breathing  the  glottis  is  rather  widely  open ;  there 
is  a  slight  movement  of  widening  at  inspiration  and  of  narrow- 
ing at  expiration. 

The  modified  respiratory  movements  of  the  larynx  in 
coughing,  hiccoughing,  yawning. 

Preceding  phonation  the  vocal  cords  are  approximated  and 
given  a  certain  degree  of  tension  by  the  action  of  the  laryn- 
geal muscles. 


—134— 

Dilation  of  the  glottis  is  produced  by  contraction  of  the 
'posterior  orico-arytenoid  muscles. 

Constriction  of  the  whole  glottis  is  brought  about  by  the 
action  of  the  arytenoid  muscle. 

Approximation  of  the  vocal  cords  may  be  brought  about 
by  the  thyro-arytenoid  muscle  :  A  similar  result  is  probably 
produced  by  contraction  of  the  lateral  crico-arytenoid  muscle. 

The  tension  of  the  vocal  cords  is  increased  chiefly  by  ac- 
tion of  the  crico-thyroid  muscle  which,  in  pulling  the  front  of 
the  cricoid  cartilage  upward,  throws  the  arytenoid  cartilage 
backward  and  increases  their  distance  from  the  anterior  attach- 
ment of  the  vocal  cords.  Contraction  of  the  posterior  crico- 
arytenoid increases  the  tension  of  the  vocal  cords. 

The  genio-hyoid  and  thyro-hyoid  muscles  when  they  con- 
tract, as  in  ascending  the  scale,  pull  the  thyroid  up  and  for- 
ward toward  the  chin  and  thus  help  render  the  vocal  cords 
tense. 

Relaxation  of  the  vocal  cords  and  opening  of  the  glottis  oc- 
curs spontaneously  in  the  resting  larynx.  Relaxation  may  be 
actively  induced  by  the  thyro-arytenoid  and  lateral  crico- 
arytenoid muscles. 

Changes  of  tension  and  position  of  the  vocal  cords  are 
probably  each  produced  by  the  combined  action  of  diiferent 
muscles. 

By  the  action  of  its  extrinsic  muscles  the  larynx  is  raised 
in  the  production  of  high  notes  and  depressed  in  the  formation 
of  low  ones.    Movements  of  the  epiglottis. 

Position  of  the  vocal  cords  in  phonation  ;  changes  of  posi- 
tion in  sounding  different  notes.  Study  by  means  of  the  laryn- 
goscope. 

Peculiar  relations  of  the  crico-thyroid  and  thyro-aryte- 
noid muscles  to  the  tension  of  the  vocal  cords. 

VOICE  PRODUCTION. 

Preliminary  to  voice  production  the  vocal  cords  are  made 
tense  and  approximated  and  the  glottis  reduced  to  a  very  nar- 
row slit  throughout  either  its  whole  extent  or  for  the  distance 
bounded  by  the  true  vocal  cords. 

Pitch  of  the  voice  is  elevated  with  increased  tension  of  the 


—135— 

vocal  cords.  Increase  in  the  strength  of  the  expiratory  blast 
somewhat  raises  the  pitch.  The  pitch  is  naturally  lower  the 
longer  the  vocal  cords. 

Quality  or  Timbre  of  the  voice  and,  largely,  its  volume  or 
strength,  are  dependent  on  the  sympathetic  vibration  of  the  air 
in  the  resonance  chambers  above  and  below  the  vocal  cords. 

The  Registers  of  the  voice  are  commonly  described  as 
three :— the  chest,  the  head  and  the  falsetto.  Their  character- 
istic differences  depend  on  combined  difference  in  the  activity 
of  the  vocal  cords  and  of  the  resonance  chambers. 

The  occurrence  and  methods  of  producton  of  the  various 
registers. 

The  range  of  the  human  voice. 

The  range  and  peculiarities  of  the  varieties  of  voice  known 
as  bass,  tenor,  alto,  soprano,  etc. 

SPEECH. 

Difference  between  whispering  and  ordinary  speech.  The 
composition  of  speech  from  vowels  and  consonants. 

The  Vowels  are  musical  sounds  produced  by  the  vibra- 
tion of  the  stretched  vocal  cords  and  whose  quality  is  deter- 
mined by  the  shape  and  size  of  the  resonance  cavities  formed 
by  the  mouth,  pharynx  and  nose.  By  the  gradual  appropriate 
change  in  these  chambers  the  whole  series  ot  vowels  may  be 
sounded  continuously. 

Classification  of  vowel  sounds  and  explanation  of  the  mode 
of  their  production. 

The  Consonants  are  noises  produced  by  peculiar  positions 
of  various  parts  of  the  vocal  apparatus.  Their  characteristic 
use  is  to  modify  the  method  of  the  beginning  or  the  ending  of 
a  vowel  sound. 

Classification  of  consonants  and  explanation  of  the  mode 
of  their  formation. 

Causes  of  the  peculiarities  of  individual  voices.  Ven- 
triloquism. 


XXV.   REPRODUCTION  AND  DEVELOPMENT. 

Living  tissues  are  continually  replacing  old  molecules  by 
new  ones.  Whole  cells  as,  e.  g.  epithelium  scales,  pass  away 
and  others  take  their  place. 

In  some  lower  animals  all  parts  of  the  body  have  extensive 
power  of  reproduction ;  the  fresh  water  hydra  ;  the  newt. 

The  phenomena  of  cell  division. 

The  object  of  reproduction  is  perpetuation   of  the  species. 

The  principles  of  heredity  and  of  variation.  Modes  of 
reproduction  ; — Simple  division  or  -fission  ;  gemmation  ;  con- 
gugation  ;  parthenogenesis  and  alternation  of  generations ; 
sexual  reproduction.    Hermaphroditism. 

REPRODUCTIVE  ORGANS  IN  THE  FEMALE. 

The  ovary.  The  ovum  in  its  OraaMan  follicle.  Develop- 
ment of  the  ovum;  germ  epithelium;  memhrana  granulosa; 
discus  proligerus.    The  corpus  luteum. 

Structure  of  the  uterus  and  of  the  Fallopian  tubes. 

Secretions  of  uterus  and  vagina. 

PUBERTY. 

The  human  male  and  female  have  reached  the  age  of 
puberty  when  first  capable  of  procreation.  In  the  female  this 
period  is  at  the  age  of  from  13  to  17  years,  though  in  warm 
climates  puberty  may  occur  at  8  years.  In  the  male  the  age  of 
puberty  is  attained  at  the  14th  to  the  16th  year. 

General  anatomical,  physiological  and  psychical  changes 
accompanying  the  advent  of  puberty. 

The  power  of  procreation  lasts  indefinitely  in  the  male, 
and  until  the  menopause  in  the  female. 

MENSTRUATION. 

From  pufterty  until  the  climacteri  or  menopause,  at  45  to  50 
years  of  age,  the  phenomenon  of  menstruation  occurs  in  the 


—138— 

female  periodically  at  intervals  of  27  to  28  days,  usually,  and 
lasts,  as  a  rule,  3  to  4  days. 

The  general  external,  physiological  and  psychical  phenom- 
ena attending  menstruation.  The  analagous  condition  of 
"  heat  "  or  "  rut  "  in  the  lower  animals. 

Changes  in  the  uterus.  Various  theories  regarding  their 
nature. 

Ovulation  and  the  changes  leading  up  to  and  attending  it. 

The  relation  between  the  occurrence  of  ovulation  and  the 
catamenial  discharge.  The  two  phenomena  are  coordinated 
but  independent.  Ovulation  before  the  appearance  of  the 
menses.  Ovulation  during  coitus  and  at  irregular  periods. 
Menstruation  after  extirpation  of  the  ovaries. 

The  sexual  centres  in  the  spinal  cord.  The  experiments  of 
Goltz. 

REPRODUCTIVE  ORGANS  IN  THE  MALE. 

The  testes  and  their  accessory  structures.  The  vesiculce 
seminales  and  their  ducts.  The  urethra  and  its  accessory 
structures. 

The  nature  and  origin  of  the  semen. 

The  anatomical  and  physiological  characters  of  the  sper- 
matozoa. 

The  physiological  mechanisms  involved  in  erection  of  the 
penis  and  in  ejaculation  of  the  semen. 

The  sexual  centres  in  the  spinal  cord.  The  experiments  of 
Goltz. 

IMPREGNATION. 

Reflex  movements  of  the  uterus  in  coitus ;  aspiration  of 
the  seminal  fluid. 

The  spermatozoon  probably  meets  and  fertilizes  the  ovum 
in  the  Fallopian  tube  or  even  at  the  ovary  itself. 

The  locomotion  of  the  spermatozoon. 

THE  PHASES  OF  LIFE. 


QP41 

Sewall 


Se8 
1888 


I 


. 


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